RF Exposure Calculator – MPE, Compliance Distance & Exclusion Zones

Q: What does this RF exposure calculator do?

It estimates the RF power density and electric and magnetic field strength produced by a transmitting antenna, compares them with the FCC, ICNIRP 2020, ICNIRP 1998 and Safety Code 6 limits, and finds the distance beyond which exposure is compliant. It also maps the exclusion zone around an elevated antenna and adds up several transmitters at one site.

Q: What is maximum permissible exposure (MPE)?

MPE is the FCC term for the highest time-averaged RF field strength or power density a person may be exposed to. ICNIRP and Safety Code 6 call the same quantity a reference level. MPE values are set so that the absorbed power in the body, the specific absorption rate (SAR), stays below the basic restriction with a safety margin.

Q: How do you calculate RF power density from a transmitter?

In the far field, S = F·EIRP/(4πR²), where EIRP is the time-averaged effective isotropic radiated power in watts, R the distance in metres and F the ground-reflection factor. The result is in W/m²; divide by 10 for mW/cm². The electric field is E = √(377·S) V/m.

Q: How do I find the safe distance from an antenna?

Set the power density equal to the limit and solve for the distance: R = √(F·EIRP/(4π·S_limit)). The limit depends on the frequency, the standard and whether the exposed people are the general public or workers. Step 3 of the calculator does this for every standard at once.

Q: What is the difference between general public and occupational limits?

Occupational (controlled) limits apply only to people exposed as part of their job who know about the exposure and can control it, for example by training, signs or switching off the transmitter. Everyone else, including passers-by and residents, falls under the general public (uncontrolled) limits, which are about five times lower in power density.

Q: Which RF exposure standard applies in my country?

The United States uses FCC 47 CFR §1.1310. Canada uses Health Canada Safety Code 6 through ISED RSS-102. The European Union recommends ICNIRP 1998 levels for the public (1999/519/EC) and sets worker action levels in Directive 2013/35/EU, and many countries have moved to ICNIRP 2020. Some countries and cities set stricter limits, so check the national regulator.

Q: What ground reflection factor should I use?

Use 2.56 for exposure near ground level, as in FCC OET Bulletin 65, which assumes the reflected field is 60 % of the direct field. Use 4 for a worst-case perfect reflection, for example over a metal roof, and 1 for free space in the main beam away from reflecting surfaces.

Q: Why does the exposure limit change with frequency?

The body absorbs RF energy most efficiently near its resonant frequencies, about 30 to 300 MHz for an adult, so the limits are lowest there. At higher frequencies the energy is absorbed closer to the surface and the limits rise, reaching a plateau in the microwave range.

Q: Is the far-field formula valid close to the antenna?

Not exactly. Inside the Fraunhofer distance 2D²/λ of a large antenna, the far-field formula overestimates the on-axis power density, so the result is conservative. Within about λ/2π of a small antenna, in the reactive near field, it can underestimate exposure and the electric and magnetic fields must be assessed separately or measured.

Q: How do duty cycle and averaging time affect the result?

The limits apply to exposure averaged over 6 or 30 minutes. A transmitter that radiates only part of the time, such as a push-to-talk radio or a TDD system, produces a lower average exposure. Enter the fraction of time it transmits as the duty cycle; use 100 % for broadcast and continuous carriers.

Step 1

Transmitter

Describe the radio and its antenna. The calculator works out the power that reaches the antenna, the time-averaged EIRP that sets exposure, and where the near field ends.

Source

Distance units

Example scenario · typical values to start from; replace with your own

Frequency

Transmitter power, per carrier

Carriers or ports

Feeder and connector loss

Operating mode · amateur radio presets

Duty cycle, time-averaged

Antenna model

Antenna gain

Largest antenna dimension

Duty cycle is the fraction of time the transmitter radiates over the averaging time (30 min for the general public under FCC and ICNIRP 2020). Use 100 % for continuous carriers and broadcast. For amateur stations, pick an operating mode and enter how many minutes you transmit and receive; the duty cycle is then the mode factor × transmit / (transmit + receive). For networks, a lower actual-power factor may apply when the operator's standard allows it.

Power budget from the transmitter to radiated power

Field regions distance from the antenna, log scale

Download

Your RF Exposure Report as a PDF

Save your assessment for your records, a site file or a client: your inputs and results, the charts and a list of official websites for learning about the regulations.

What the report contains

Summary: pass or fail at your distance, percentage of the limit and the compliance distance
Transmitter: power budget, EIRP, ERP and field regions
Limits and distances: every standard and tier at your frequency, plus the FCC exemption tests
Site and multiple sources: the exclusion-zone map and the total exposure ratio
Learn more: official regulator and standards websites (FCC, ICNIRP, EU, Health Canada, ISED, IEEE, IEC, ITU) with links

A4, about 7 pages. Built in your browser; nothing is uploaded.

About this RF exposure calculator

This free calculator from NextAntennas estimates human exposure to radio-frequency fields from a transmitting antenna. It computes the power density and the electric and magnetic field strength, compares them with the maximum permissible exposure (MPE) or reference levels of FCC 47 CFR §1.1310, ICNIRP 2020, ICNIRP 1998 (EU Council Recommendation 1999/519/EC) and Health Canada Safety Code 6 (ISED RSS-102), and finds the compliance distance for the general public and for workers.

How to use it

Transmitter: enter the frequency, transmitter power, number of carriers, feeder loss, antenna gain and duty cycle, or pick an amateur operating mode (SSB, CW, FM, digital) with transmit and receive minutes. Distances can be shown in metres or feet. Choose the point-source model for most antennas or the circular-aperture model for a dish.
Exposure limits: pick the standard and the tier; the limits at your frequency and across 0.3 MHz to 100 GHz are shown.
Compliance distance: power density, E, H and percentage of the limit at any distance, the safe distance for every standard, and the FCC §1.1307(b)(3) exemption tests.
Site exclusion zone: a to-scale side view of an elevated sector antenna with downtilt, showing where exposure exceeds the limit and how much reaches people at ground level.
Multiple sources: add co-located transmitters and check the total exposure ratio.

RF exposure equations

Far-field power density S = F·EIRP/(4πR²), with EIRP = P·G·(duty cycle) after feeder loss and F the ground-reflection factor. Field strength E = √(377·S) and H = √(S/377). The compliance distance is R = √(F·EIRP/(4π·S_limit)). For a dish of diameter D, the OET-65 near-field power density is 16ηP/(πD²) out to D²/(4λ).

Regulations and FAQ

Full reference-level tables for every standard, with their sources, are in Rules, Limits and Regulations, and answers to common questions are in the FAQ below.

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Engineering Theory

Theory Behind the Equations

How the calculator works: from transmitter power to time-averaged EIRP, from EIRP to power density and field strength, and from there to the limits, the compliance distance and the exclusion zone.

1. What Is RF Exposure?

Radio-frequency fields above about 100 kHz deposit energy in the body as heat. Exposure standards limit that heating with a margin: the basic restriction is the specific absorption rate (SAR) in W/kg, or, above 6 GHz, the absorbed power density at the skin. SAR is hard to measure, so the standards also give reference levels, called maximum permissible exposure (MPE) by the FCC, in quantities you can calculate and measure outside the body: power density S in W/m² and the field strengths E in V/m and H in A/m.

The reference levels are set so that a person standing in a uniform field at the limit stays below the basic restriction. Meeting them is sufficient for compliance; exceeding them means a closer look, not necessarily a breach of the basic restriction. Every value is an average over time (6 or 30 minutes) and, in most standards, over the body.

2. From Transmitter Power to Time-Averaged EIRP

Exposure depends on the power the antenna radiates in the direction of the person, averaged over the standard's averaging time:

Effective isotropic radiated power

{EIRP}_{avg} = N P_{tx} \cdot 10^{- L / 10} \cdot G_{i} \cdot δ

N = carriers or ports · P_tx = power per carrier · L = feeder loss in dB · G_i = gain relative to isotropic · δ = duty cycle

Gain quoted in dBd is relative to a half-wave dipole: G_dBi = G_dBd + 2.15. The effective radiated power used in FCC exemption rules is ERP = EIRP / 1.64.

3. Far-Field Power Density and Ground Reflection

In the far field the power spreads over a sphere, so the power density falls with the square of the distance:

Far-field power density (OET-65)

S = \frac{F \cdot {EIRP}_{avg}}{4 π R^{2}}

R = distance in metres · S in W/m² (1 mW/cm² = 10 W/m²)

A wave reflected from the ground can add in phase to the direct wave. If the reflected field is a fraction Γ of the direct field, the power density rises by |1 + Γ|². OET-65 uses Γ = 0.6 for ground-level estimates, giving F = 2.56; F = 4 is the perfect-reflection worst case, and F = 1 applies in free space in the main beam.

4. Electric and Magnetic Field Strength

In the far field E and H are in phase and their ratio is the impedance of free space, η₀ ≈ 377 Ω:

Plane-wave relations

E = \sqrt{η_{0} S}

H = \sqrt{\frac{S}{η_{0}}}

S = E H

All RMS values

At low frequencies several standards give only E and H limits. The calculator converts them to a plane-wave equivalent power density and uses the stricter of E²/η₀ and η₀H², because both must be met.

5. Compliance Distance

Setting S equal to the limit and solving for R gives the distance beyond which the main-beam exposure is compliant:

Compliance distance, point source

R_{c} = \sqrt{\frac{F \cdot {EIRP}_{avg}}{4 π S_{\lim} (f)}}

For the aperture model the calculator solves the same condition numerically on the piecewise near-field, transition and far-field curve of section 7.

6. Field Regions

The far-field formula assumes the person is far enough away that the antenna looks like a point. For an antenna whose largest dimension is D:

Region boundaries

R_{reactive} = 0.62 \sqrt{\frac{D^{3}}{λ}}

R_{Fraunhofer} = \frac{2 D^{2}}{λ}

For an antenna small compared with λ, the reactive region extends to about λ/2π

Inside the Fraunhofer distance of a large antenna the beam has not formed, so the far-field formula overestimates the on-axis power density and the result is conservative. Inside the reactive near field of a small antenna the formula can underestimate the fields, and E and H must be evaluated separately.

7. Aperture Antennas — the OET-65 Dish Model

For a circular aperture of diameter D and efficiency η, OET-65 bounds the on-axis power density in three regions:

Near field, transition, far field

S_{nf} = \frac{16 η P}{π D^{2}}

S_{t} = \frac{S_{nf} R_{nf}}{R}

S_{ff} = \frac{G P}{4 π R^{2}}

R_nf = D²/(4λ) · far field from R_ff = 0.6D²/λ · G = η(πD/λ)² · P = time-averaged power at the feed

The near-field value is about four times the average power density over the aperture, and it holds as a plateau out to R_nf. The aperture formulas describe the main beam and include no ground reflection; off axis the power density is much lower.

8. The Limits

The four standards share a shape: a plateau at VHF where the human body resonates (about 30–300 MHz), a rise with frequency through the UHF bands as absorption becomes shallower, and a second plateau in the microwave range. The FCC general-population MPE, for example:

Frequency (MHz)	E (V/m)	H (A/m)	S (mW/cm²)	Averaging
0.3 – 1.34	614	1.63	100*	30 min
1.34 – 30	824/f	2.19/f	180/f²*	30 min
30 – 300	27.5	0.073	0.2	30 min
300 – 1500	—	—	f/1500	30 min
1500 – 100 000	—	—	1.0	30 min

* plane-wave equivalent. Occupational limits are five times the power density (6-minute average). ICNIRP 2020 sets 2 W/m² at 30–400 MHz, f/200 W/m² at 400–2000 MHz and 10 W/m² above 2 GHz for the public, averaged over 30 minutes; ICNIRP 1998 has the same power densities above 10 MHz with a 6-minute average. Safety Code 6 follows a smoother curve, 0.02619·f^0.6834 W/m² from 300 MHz to 6 GHz, which is lower than the other three in the cellular bands.

9. Several Transmitters

Heating from different frequencies adds, so each source is weighted by the limit at its own frequency:

Total exposure ratio

TER = \sum_{i} \frac{S_{i}}{S_{\lim} (f_{i})} \leq 1

This thermal summation applies above about 10 MHz. At lower frequencies ICNIRP also sums field strengths for nerve-stimulation effects, which this calculator does not do. Under FCC rules, a transmitter that contributes less than 5 % of its limit at a point of non-compliance is not responsible for it.

10. FCC Exemptions — 47 CFR §1.1307(b)(3)

A single transmitter needs no routine evaluation if it meets one of three tests. The 1 mW test: available time-averaged power no more than 1 mW. The SAR-based test, for 0.3–6 GHz at separations up to 40 cm:

SAR-based threshold

P_{th} = {ERP}_{20cm} {(\frac{d}{20})}^{x}

x = - \log_{10} (\frac{60}{{ERP}_{20cm} \sqrt{f}})

d in cm (≤ 20; between 20 and 40 cm P_th = ERP_20cm) · f in GHz · ERP_20cm = 2040f mW below 1.5 GHz, 3060 mW from 1.5 to 6 GHz

The power compared is the greater of the available power and the ERP. The MPE-based test applies at R ≥ λ/2π and compares ERP with 1920R² W (0.3–1.34 MHz), 3450R²/f² (1.34–30 MHz), 3.83R² (30–300 MHz), 0.0128R²f (300–1500 MHz) and 19.2R² (1.5–100 GHz), with R in metres and f in MHz.

11. Validity and Limitations

The calculator gives conservative planning estimates for whole-body exposure in the far field. Note:

It does not compute SAR or local (partial-body) exposure; for devices held within 20 cm of the body a SAR evaluation applies.
The point-source model can underestimate exposure in the reactive near field of a small antenna and overestimates it inside the Fraunhofer distance of a large one.
The site view uses a generic vertical pattern; use the manufacturer's pattern for a final assessment, and include the horizontal pattern, mechanical tilt and building attenuation where they matter.
Local rules can be stricter than the standards listed, and the 5G and above-6 GHz provisions of ICNIRP 2020 and Safety Code 6 (local exposure over 4 cm² or 1 cm²) are not covered.

Verify any site where people can enter the computed exclusion zone by measurement.

References

U.S. Code of Federal Regulations, 47 CFR §1.1307(b) and §1.1310, Radiofrequency radiation exposure limits.
FCC Office of Engineering and Technology, OET Bulletin 65: Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, ed. 97-01, 1997.
FCC, Resolution of Notice of Inquiry, Second Report and Order, FCC 19-126, 2019.
ICNIRP, “Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz),” Health Physics, vol. 118, no. 5, pp. 483–524, 2020.
ICNIRP, “Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (up to 300 GHz),” Health Physics, vol. 74, no. 4, pp. 494–522, 1998.
Council of the European Union, Recommendation 1999/519/EC on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz), 1999.
Health Canada, Safety Code 6: Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz, 2015.
Innovation, Science and Economic Development Canada, RSS-102: Radio Frequency (RF) Exposure Compliance of Radiocommunication Apparatus.
IEC 62232, Determination of RF field strength, power density and SAR in the vicinity of radiocommunication base stations for the purpose of evaluating human exposure.
3GPP TR 36.814, Further advancements for E-UTRA physical layer aspects, antenna pattern model.
Balanis, C.A., Antenna Theory: Analysis and Design, 4th ed., Wiley, 2016.

Regulatory Reference

Rules, Limits and Regulations

The standards this calculator applies, their full reference-level tables, the SAR limits they protect, the FCC exemption thresholds and the assessment rules, each with its source. Check the current text of the regulation that applies to your site before relying on a value.

Standards and Regulations at a Glance

Table R1. Exposure rules, standards and guidance used in this calculator
Rule or standard	Where it applies	Scope	Tiers	Reference
FCC MPE limits	United States	0.3 MHz – 100 GHz, power density and field strength	General population / uncontrolled; occupational / controlled	47 CFR §1.1310, Table 1; FCC 19-126 (2019)
FCC environmental rules and exemptions	United States	When an RF evaluation is required; exemption thresholds; multiple-transmitter sites	As above	47 CFR §1.1307(b)
FCC device rules	United States	Mobile devices (≥ 20 cm) and portable devices (< 20 cm), SAR limits	As above	47 CFR §2.1091, §2.1093
FCC evaluation guide	United States	Prediction formulas, aperture models, ground reflection, measurement	—	FCC OET Bulletin 65, ed. 97-01
ICNIRP 2020	International; adopted in national rules by many countries	100 kHz – 300 GHz; basic restrictions and reference levels	General public; occupational	ICNIRP, Health Physics 118(5):483–524, 2020
ICNIRP 1998	International; basis of EU and many national rules	Up to 300 GHz; basic restrictions and reference levels	General public; occupational	ICNIRP, Health Physics 74(4):494–522, 1998
EU Council Recommendation	European Union, general public	0 Hz – 300 GHz, ICNIRP 1998 public levels	General public	Council Recommendation 1999/519/EC
EU EMF Directive	European Union, workers	0 Hz – 300 GHz, action levels based on ICNIRP 1998 occupational	Workers	Directive 2013/35/EU
Safety Code 6	Canada	3 kHz – 300 GHz; basic restrictions and reference levels	Uncontrolled; controlled environment	Health Canada, Safety Code 6 (2015)
RSS-102	Canada, radio equipment certification	Applies Safety Code 6 to devices; exemption limits and evaluation methods	As Safety Code 6	ISED RSS-102
IEEE C95.1	Consensus standard; referenced by US agencies	0 Hz – 300 GHz (not computed in this calculator)	Unrestricted; restricted environment	IEEE Std C95.1-2019
Base-station assessment	International	Methods to compute and measure exposure near base stations and define compliance boundaries	—	IEC 62232; ITU-T K.52, K.70, K.100
Device SAR measurement	International	Measurement of SAR from hand-held and body-worn devices	—	IEC/IEEE 62209-1528

Official sourceseCFR 47 CFR §1.1310 ↗eCFR §1.1307 ↗ICNIRP 2020 ↗EU 1999/519/EC ↗Safety Code 6 ↗RSS-102 Issue 6 notice ↗

Reference Levels by Standard

Table R2. FCC maximum permissible exposure (MPE)

General public
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.3 – 1.34	614	1.63	1000*	30 min
1.34 – 30	824/f	2.19/f	1800/f²*	30 min
30 – 300	27.5	0.073	2	30 min
300 – 1500	—	—	f/150	30 min
1500 – 100 000	—	—	10	30 min

Occupational
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.3 – 3	614	1.63	1000*	6 min
3 – 30	1842/f	4.89/f	9000/f²*	6 min
30 – 300	61.4	0.163	10	6 min
300 – 1500	—	—	f/30	6 min
1500 – 100 000	—	—	50	6 min

* plane-wave equivalent power density. Reference: 47 CFR §1.1310, Table 1 (values stated there in mW/cm²). f in MHz. E and H are RMS; S is plane-wave equivalent power density (1 mW/cm² = 10 W/m²).

Official sourceseCFR 47 CFR §1.1310 ↗FCC 19-126, Federal Register 2020 ↗FCC OET Bulletin 65 ↗

Table R3. ICNIRP 2020 reference levels, whole body

General public
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.1 – 30	300/f^0.7	2.2/f	—	30 min
30 – 400	27.7	0.073	2	30 min
400 – 2000	1.375 f^0.5	0.0037 f^0.5	f/200	30 min
2000 – 300 000	—	—	10	30 min

Occupational
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.1 – 30	660/f^0.7	4.9/f	—	30 min
30 – 400	61	0.16	10	30 min
400 – 2000	3 f^0.5	0.008 f^0.5	f/40	30 min
2000 – 300 000	—	—	50	30 min

Local exposure (Table 6, 6-minute average) and brief-exposure limits (Table 7) also apply and are not computed here. Reference: ICNIRP (2020), Table 5. f in MHz. E and H are RMS; S is plane-wave equivalent power density (1 mW/cm² = 10 W/m²).

Official sourcesICNIRP RF guidelines 2020 ↗ICNIRP 2020 full text (PDF) ↗

Table R4. ICNIRP 1998 reference levels (EU 1999/519/EC for the public)

General public
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.15 – 1	87	0.73/f	—	6 min
1 – 10	87/f^0.5	0.73/f	—	6 min
10 – 400	28	0.073	2	6 min
400 – 2000	1.375 f^0.5	0.0037 f^0.5	f/200	6 min
2000 – 300 000	61	0.16	10	6 min†

Occupational
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
0.065 – 1	610	1.6/f	—	6 min
1 – 10	610/f	1.6/f	—	6 min
10 – 400	61	0.16	10	6 min
400 – 2000	3 f^0.5	0.008 f^0.5	f/40	6 min
2000 – 300 000	137	0.36	50	6 min†

† above 10 GHz the averaging time is 68/f_GHz^1.05 minutes. Reference: ICNIRP (1998), Tables 6 and 7; Council Recommendation 1999/519/EC, Annex III. f in MHz. E and H are RMS; S is plane-wave equivalent power density (1 mW/cm² = 10 W/m²).

Official sourcesEU Recommendation 1999/519/EC (EU-OSHA) ↗Directive 2013/35/EU (EUR-Lex) ↗ICNIRP publications ↗

Table R5. Health Canada Safety Code 6 reference levels, 10 MHz – 300 GHz

General public
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
10 – 20	27.46	0.0728	2	6 min
20 – 48	58.07/f^0.25	0.1540/f^0.25	8.944/f^0.5	6 min
48 – 300	22.06	0.05852	1.291	6 min
300 – 6000	3.142 f^0.3417	0.008335 f^0.3417	0.02619 f^0.6834	6 min
6000 – 15 000	61.4	0.163	10	6 min
15 000 – 150 000	61.4	0.163	10	616000/f^1.2 min
150 000 – 300 000	0.158 f^0.5	4.21×10⁻⁴ f^0.5	6.67×10⁻⁵ f	616000/f^1.2 min

Occupational
Frequency (MHz)	E (V/m)	H (A/m)	S (W/m²)	Averaging
10 – 20	61.4	0.163	10	6 min
20 – 48	129.8/f^0.25	0.3444/f^0.25	44.72/f^0.5	6 min
48 – 100	49.33	0.1309	6.455	6 min
100 – 6000	15.60 f^0.25	0.04138 f^0.25	0.6455 f^0.5	6 min
6000 – 15 000	137	0.364	50	6 min
15 000 – 150 000	137	0.364	50	616000/f^1.2 min
150 000 – 300 000	0.354 f^0.5	9.40×10⁻⁴ f^0.5	3.33×10⁻⁴ f	616000/f^1.2 min

Uncontrolled environment (left) and controlled environment (right). Below 10 MHz Safety Code 6 also sets nerve-stimulation limits, not computed here. Reference: Health Canada, Safety Code 6 (2015), Tables 5 and 6; applied to devices by ISED RSS-102. f in MHz. E and H are RMS; S is plane-wave equivalent power density (1 mW/cm² = 10 W/m²).

Official sourcesHealth Canada Safety Code 6 ↗ISED Radio Standards Specifications ↗RSS-102 Issue 6 notice ↗

Basic Restrictions (SAR)

The reference levels above are set so that a person in a uniform field at the limit stays below these absorbed-power limits, with a margin.

Table R6. Basic restrictions (SAR) that the reference levels protect
Quantity	FCC (public / occupational)	ICNIRP 2020 (public / occupational)	Safety Code 6 (uncontrolled / controlled)
Whole-body average SAR	0.08 / 0.4 W/kg	0.08 / 0.4 W/kg	0.08 / 0.4 W/kg
Local SAR, head and trunk	1.6 / 8 W/kg, over 1 g	2 / 10 W/kg, over 10 g	1.6 / 8 W/kg, over 1 g
Local SAR, limbs or extremities	4 / 20 W/kg, over 10 g	4 / 20 W/kg, over 10 g	4 / 20 W/kg, over 10 g
Applies to	Portable devices, 47 CFR §2.1093	100 kHz – 6 GHz	Devices and near-field exposure

References: 47 CFR §1.1310 and §2.1093; ICNIRP (2020), Table 2; Health Canada Safety Code 6 (2015), Table 3.

Official sourceseCFR 47 CFR §2.1093 ↗eCFR §2.1091 ↗ICNIRP 2020 (PDF) ↗Safety Code 6 ↗IEC/IEEE 62209-1528 ↗

FCC Exemption Thresholds

Table R7. FCC exemption from routine RF evaluation (R in m, f in MHz, d in cm)
Test	Applies	Threshold	Reference
1 mW blanket exemption	Any frequency, separation > 0.5 cm	Available time-averaged power ≤ 1 mW	47 CFR §1.1307(b)(3)(i)(A)
SAR-based exemption	0.3 – 6 GHz, 0.5 – 40 cm	P_th = ERP_20cm(d/20)^x for d ≤ 20 cm, ERP_20cm for 20 – 40 cm; ERP_20cm = 2040f mW (f < 1.5 GHz) or 3060 mW (1.5 – 6 GHz)	47 CFR §1.1307(b)(3)(i)(B)
MPE-based, 0.3 – 1.34 MHz	R ≥ λ/2π	ERP ≤ 1920 R² W	47 CFR §1.1307(b)(3)(i)(C)
MPE-based, 1.34 – 30 MHz	R ≥ λ/2π	ERP ≤ 3450 R²/f² W	as above
MPE-based, 30 – 300 MHz	R ≥ λ/2π	ERP ≤ 3.83 R² W	as above
MPE-based, 300 – 1500 MHz	R ≥ λ/2π	ERP ≤ 0.0128 R² f W	as above
MPE-based, 1.5 – 100 GHz	R ≥ λ/2π	ERP ≤ 19.2 R² W	as above

Official sourceseCFR 47 CFR §1.1307 ↗FCC 19-126, Federal Register 2020 ↗

How the Limits Are Applied

Table R8. Assessment rules that decide how the limits are applied
Rule	What it says	Reference
Time averaging	Exposure is averaged over 30 min (public) or 6 min (occupational) under FCC; 30 min whole-body under ICNIRP 2020; 6 min under ICNIRP 1998 and Safety Code 6 below 10–15 GHz.	47 CFR §1.1310; ICNIRP 2020 §4; Safety Code 6 §2
Occupational tier	Higher limits apply only to people exposed through their work who are aware of the exposure and can exercise control over it. Everyone else is in the public tier.	47 CFR §1.1310; ICNIRP 2020; Safety Code 6
Multiple sources	Each source is expressed as a fraction of its own frequency's limit and the fractions are added; the total must not exceed 100 %.	47 CFR §1.1307(b); ICNIRP 2020 §5; Safety Code 6 §2.2
5 % contribution	At an FCC multi-transmitter site, a transmitter producing less than 5 % of its limit in an area that exceeds the total limit is not responsible for bringing it into compliance.	47 CFR §1.1307(b)
Spatial averaging	Field values may be averaged over the space occupied by the body (typically 0–2 m height) where the field is non-uniform; peak values must still respect local limits.	OET Bulletin 65; ICNIRP 2020; IEC 62232
Ground reflection	Prediction near ground level uses a reflection factor of 2.56 (\|1 + 0.6\|²); 4 is the worst case.	OET Bulletin 65, §2
Mobile vs portable devices	Devices used ≥ 20 cm from the body are evaluated against MPE; closer than 20 cm, against SAR.	47 CFR §2.1091, §2.1093
Controlling access	Where limits can be exceeded, the licensee must restrict access with signs, barriers, training or power reduction.	47 CFR §1.1307(b); Directive 2013/35/EU

Official sourceseCFR §1.1307 ↗eCFR §1.1310 ↗OET Bulletin 65 ↗ICNIRP 2020 ↗Safety Code 6 ↗Directive 2013/35/EU ↗IEC 62232 ↗

FAQ

Frequently Asked Questions

Common questions about RF exposure limits, safe distances and how to use this calculator.

What does this RF exposure calculator do?

It estimates the RF power density and electric and magnetic field strength produced by a transmitting antenna, compares them with the FCC, ICNIRP 2020, ICNIRP 1998 and Safety Code 6 limits, and finds the distance beyond which exposure is compliant. It also maps the exclusion zone around an elevated antenna and adds up several transmitters at one site.

What is maximum permissible exposure (MPE)?

MPE is the FCC term for the highest time-averaged RF field strength or power density a person may be exposed to. ICNIRP and Safety Code 6 call the same quantity a reference level. MPE values are set so that the absorbed power in the body, the specific absorption rate (SAR), stays below the basic restriction with a safety margin.

How do you calculate RF power density from a transmitter?

In the far field, S = F·EIRP/(4πR²), where EIRP is the time-averaged effective isotropic radiated power in watts, R the distance in metres and F the ground-reflection factor. The result is in W/m²; divide by 10 for mW/cm². The electric field is E = √(377·S) V/m.

How do I find the safe distance from an antenna?

Set the power density equal to the limit and solve for the distance: R = √(F·EIRP/(4π·S_limit)). The limit depends on the frequency, the standard and whether the exposed people are the general public or workers. Step 3 of the calculator does this for every standard at once.

What is the difference between general public and occupational limits?

Occupational (controlled) limits apply only to people exposed as part of their job who know about the exposure and can control it, for example by training, signs or switching off the transmitter. Everyone else, including passers-by and residents, falls under the general public (uncontrolled) limits, which are about five times lower in power density.

Which RF exposure standard applies in my country?

The United States uses FCC 47 CFR §1.1310. Canada uses Health Canada Safety Code 6 through ISED RSS-102. The European Union recommends ICNIRP 1998 levels for the public (1999/519/EC) and sets worker action levels in Directive 2013/35/EU, and many countries have moved to ICNIRP 2020. Some countries and cities set stricter limits, so check the national regulator.

What ground reflection factor should I use?

Use 2.56 for exposure near ground level, as in FCC OET Bulletin 65, which assumes the reflected field is 60 % of the direct field. Use 4 for a worst-case perfect reflection, for example over a metal roof, and 1 for free space in the main beam away from reflecting surfaces.

Why does the exposure limit change with frequency?

The body absorbs RF energy most efficiently near its resonant frequencies, about 30 to 300 MHz for an adult, so the limits are lowest there. At higher frequencies the energy is absorbed closer to the surface and the limits rise, reaching a plateau in the microwave range.

Is the far-field formula valid close to the antenna?

Not exactly. Inside the Fraunhofer distance 2D²/λ of a large antenna, the far-field formula overestimates the on-axis power density, so the result is conservative. Within about λ/2π of a small antenna, in the reactive near field, it can underestimate exposure and the electric and magnetic fields must be assessed separately or measured.

How do duty cycle and averaging time affect the result?

The limits apply to exposure averaged over 6 or 30 minutes. A transmitter that radiates only part of the time, such as a push-to-talk radio or a TDD system, produces a lower average exposure. Enter the fraction of time it transmits as the duty cycle; use 100 % for broadcast and continuous carriers.

How are several transmitters at one site combined?

Divide each transmitter's power density by the limit at its own frequency and add the fractions. The site complies if the total exposure ratio is 100 % or less. Step 5 of the calculator does this and shows which source contributes most.

When is a transmitter exempt from an FCC RF evaluation?

Under 47 CFR §1.1307(b)(3) a single transmitter is exempt if its available power is at most 1 mW, if its power is below the SAR-based threshold for its frequency and separation (0.3 to 6 GHz, up to 40 cm), or if its ERP is below the MPE-based threshold for its distance. Step 3 runs all three tests.

Does the calculator compute SAR?

No. It works with power density and field strength, which apply when the person is in the far field of the antenna. Phones, wearables and other devices used within 20 cm of the body need a SAR evaluation, normally by measurement to IEC/IEEE 62209-1528 or by simulation.

Do the limits cover 5G and millimetre-wave frequencies?

Yes. All four standards extend to 100 or 300 GHz and the calculator covers 0.3 MHz to 100 GHz. Above 6 GHz, ICNIRP 2020 and Safety Code 6 add limits on local power density averaged over small skin areas, which this calculator does not compute.

Can I use the results as a compliance report?

Use them for planning, site design and to decide whether an evaluation is needed. A compliance record normally requires an assessment to a recognized method such as IEC 62232 or OET Bulletin 65, using the manufacturer's antenna patterns, or a calibrated RF survey.

Transmitter

Source

Power budget from the transmitter to radiated power

Field regions distance from the antenna, log scale

Exposure limits

Power density limit against frequency GeneralOccupational

All limits at your frequency Copy as CSV

Compliance distance

Power density against distance main beam, log–log

Compliance distance by standard Copy as CSV

FCC exemption check 47 CFR §1.1307(b)(3), single fixed or mobile transmitter

Site exclusion zone

Exposure map percentage of the selected limit, side view

At the evaluation height percentage of the limit against horizontal distance

Multiple sources

Sources Add sourceAdd the step 1 transmitterCopy as CSV