Methodology: how the EMF calculator works

Last reviewed: 19 October 2026

The calculator on the homepage turns a list of devices, distances and daily habits into an estimated exposure figure for each frequency band, expressed as a percentage of the reference level the site applies for that band. This page explains each step of that calculation, the standards it compares against, and — just as important — what the result does not mean. The short version is on the About page; this is the full method.

Step 1: You choose the standards for each band

Fields are grouped into seven bands, and each band is compared against a reference level drawn from published guidance:

• Static fields (DC, 0 Hz) — 1000 µT, combining WHO occupational exposure limits with the Earth's natural field baseline.
• Extremely low frequency (ELF, 3–30 Hz) — 200 µT, the general public exposure limit for ELF magnetic fields.
• Power frequency (AC, 50–60 Hz) — 0.35 µT, a balanced average of WHO, EU, NIEHS and ARPANSA guidelines.
• Low frequency (LF, 100 kHz) — 27 µT, the public exposure limit for low-frequency fields.
• Medium frequency (MF, 300 kHz–30 MHz) — 0.92 W/m², public exposure limits for medium/high-frequency fields, relevant near broadcast and industrial sources.
• Radio frequency (RF, 1.5–300 GHz) — 10 W/m², the US public exposure limit for RF radiation, covering cellular networks, WiFi and 5G.
• Ionizing radiation (above 2.4 PHz) — 1 mSv/year, the international recommended limit for artificial radiation exposure.

Where the underlying guidelines differ by authority, the page says which authority's figure is in use rather than blending them silently; the power-frequency band is the one deliberate exception, and it is labelled as an average.

Step 2: Sources are added with position and mode factors

Each source you select — a phone, a WiFi router, a power line, an appliance — starts from a published emission range for that class of device. The calculator then adjusts for how the device is actually used: a phone on a call against the head is not the same exposure as the same phone idle in a bag, so position and mode factors scale the emission range before anything is summed. Presets (Urban, Rural, Tech Worker, Train Commuter, EV Commuter) are simply saved combinations of sources, distances and usage patterns built from the same pieces; choosing one changes the inputs, never the method.

Step 3: Distance fall-off is applied where distance exists

Field strength drops quickly with distance, and the fall-off law depends on the source:

• Power lines — inverse-cube within 20 m, inverse-square beyond.
• Transformer stations — inverse-square beyond 10 m, held constant closer in.
• AM transmitters — inverse-distance.

This is why distance is the most powerful input you control. How much a doubling buys depends on the law that applies: to a quarter under inverse-square (power lines beyond 20 m, transformer stations beyond 10 m), to an eighth under the power-line inverse-cube branch within 20 m, and to a half under the AM inverse-distance law. Sources without a distance input — phones are the main one — are adjusted by the position and mode factors in Step 2 instead. Everyday guidance follows from the physics — a wired headset moves the phone away from your head, and a router across the room exposes you to far less than the same router on the desk beside you.

Step 4: Results are compared band by band

For each band, the summed, distance-adjusted estimate is shown next to that band's reference level and as a percentage of it. Bands are never merged into a single score: a percentage for power-frequency magnetic fields and a percentage for RF power density measure different physical quantities against different guidelines, and adding them together would be meaningless. For context, typical home magnetic-field backgrounds run about 0.01–0.3 µT, far below the 200 µT ICNIRP public reference level at power frequency (ICNIRP, 2010).

What the estimate is not

• Not a measurement. The model works from published emission ranges and your inputs. A calibrated meter at the actual location will give a different, more accurate number for that spot.
• Not medical advice. Current scientific evidence has not consistently demonstrated established adverse health effects at exposure levels below international guideline limits, and a 2024 WHO-commissioned systematic review found no association between mobile-phone use and brain cancer. The calculator exists to inform, not to diagnose or to alarm.
• Not a product. Nothing here is for sale, and the method is why the site is blunt about consumer "EMF blockers" — stickers, chips and pendants do not change any term in the equations above. Distance and time do.

Sources

Every factual claim on this page carries a dated citation:

• ICNIRP (2010), "Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz)", Health Physics 99(6): 818–836.
• ICNIRP (2020), "Guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz)", Health Physics 118(5): 483–524.
• IARC (2002), Monographs Vol. 80 — ELF magnetic fields: Group 2B "possibly carcinogenic".
• IARC (2011), Monographs Vol. 102 — RF electromagnetic fields: Group 2B.
• WHO (2007), Environmental Health Criteria 238: Extremely low frequency (ELF) fields.
• Karipidis et al. (2024), Environment International — WHO-commissioned systematic review of RF and cancer risk in human studies.

The per-source pages — WiFi routers, mobile phones, power lines, household appliances, smart meters, baby monitors and 5G small cells — apply this same method source by source, with the transmit-power caps and limits specific to each. Corrections are welcome: if a figure here does not match the cited source edition, tell us via the contact page and we will check it.