How to Read an EMF Detector: Units and Normal Levels

To read an EMF detector, first check which kind of field it measures, because the units tell you: radio-frequency (RF) meters show power density in µW/m² or mW/m² (sometimes electric field in V/m), while low-frequency meters show magnetic field in microtesla (µT) or milligauss (mG) and electric field in volts per metre (V/m). Then compare your reading with a quiet background spot in the same home, not with a number from the internet, and note whether the display shows a peak or an average value.

This guide explains the units, what "normal" readings look like, how to use an EMF meter properly and how to test that yours is working.

How do EMF detectors work?

An EMF detector is a small receiver. Inside are antennas or sensor coils tuned to a frequency range, plus electronics that convert the signal into a number or a row of lights.

• RF meters pick up signals from Wi-Fi routers, mobile phones, masts, smart meters and Bluetooth, typically somewhere between a few hundred megahertz and several gigahertz.
• Low-frequency (ELF) meters measure the 50 Hz fields from mains wiring, appliances and power lines. Magnetic fields are sensed by coils; electric fields by a plate or probe.
• Combined meters measure more than one type, usually with a switch or separate display for each.

That's why one meter may show almost nothing next to a router while another lights up: they're looking at different things. Our guide on which EMF meter you need explains how to choose between RF and low-frequency models.

EMF meter units explained

RF readings: µW/m², mW/m² and V/m

Power density is the amount of radio-frequency energy passing through an area. You'll see it in microwatts per square metre (µW/m²) or milliwatts per square metre (mW/m²); 1 mW/m² equals 1,000 µW/m². Some meters show electric field strength in V/m instead. The two are linked: 1 V/m is roughly 2,650 µW/m².

Magnetic field readings: µT and mG

Low-frequency magnetic fields are shown in microtesla (µT) or milligauss (mG). The conversion is simple: 1 µT = 10 mG. So a reading of 2 mG is 0.2 µT.

Electric field readings: V/m

For 50 Hz electric fields, the unit is also V/m, but it's measuring something different from an RF meter's V/m. Low-frequency electric fields come from wiring and plugged-in cables even when an appliance is switched off, and they're strongly affected by whether you and the meter are grounded.

What are normal EMF levels in a UK home?

There isn't a single "normal" figure, because readings vary by room, time of day and distance from sources. As a guide:

• Magnetic fields in the middle of most rooms are a small fraction of a microtesla, rising sharply within a few centimetres of appliances such as microwaves, hairdryers and transformers, then dropping away quickly with distance.
• RF levels are usually highest near an active router, a phone during a call or download, or a smart meter as it transmits, and lower elsewhere.
• Electric fields tend to be highest near ungrounded lamp cables, extension leads and walls with wiring behind them.

For context, international public exposure guidelines from ICNIRP are far higher than typical home readings: 200 µT for 50 Hz magnetic fields, and for RF from about 4.5 W/m² at 900 MHz up to 10 W/m² above 2 GHz (that's 10,000,000 µW/m²). Many people who measure EMF choose their own, much lower, personal targets; whatever you decide, a consistent baseline matters more than any one number.

Real-world surveys help put numbers in perspective. In 2025 the UK Health Security Agency published measurements taken near 56 active 5G masts at 30 locations across the UK. Total RF exposure was well within ICNIRP's public reference levels, even in a worst-case extrapolation, and 4G, not 5G, was the biggest contributor, with 5G adding on average less than 10%. It's a useful reminder that a meter reading near a mast usually reflects several networks at once, not just the newest one.

How to use an EMF meter: step by step

1. Read the manual for the display mode. Find out whether it shows peak, maximum hold or average values. Peak readings jump around with pulsed signals like Wi-Fi; averages are steadier.
2. Put your own phone in aeroplane mode, or leave it in another room, so it doesn't dominate the reading.
3. Take a background reading in the quietest spot you can find, away from appliances and windows. Write it down.
4. Hold the meter at arm's length and keep your hand clear of the sensor area. Your body can block or reflect RF.
5. Move slowly. Sweep each room at chest or bed height, pausing for a few seconds at each spot. Rotate a single-axis meter to find the highest value.
6. Repeat at different times. Wi-Fi traffic, neighbours' devices and mains loads change through the day.
7. Log your readings with the location, time and what was switched on, so you can compare before and after any changes.

For a full room-by-room survey routine, see our guide to finding radiation hotspots in your home.

How to test an EMF meter is working

Misuratore RF ricaricabile Safe and Sound Pro II 200 MHz – 8 GHz

You don't need lab equipment to check a meter responds properly. Use known sources and watch for a clear change:

• RF meter: start a large download on your phone or a video call, hold the meter 30 cm away, then switch the phone to aeroplane mode. Readings should rise and then fall.
• Router test: walk towards your Wi-Fi router while it's busy streaming. The reading should increase as you get closer.
• Magnetic field meter: hold it near a running hairdryer or microwave, then switch it off. The value should drop back towards your background reading.
• Electric field meter: hold it near a plugged-in lamp cable, then unplug the lamp at the wall.
• Zero check: in a quiet spot, the meter should settle to a low, steady reading. If it never settles, check the battery.

If a meter doesn't respond to any of these, it may be outside its frequency range, faulty or set to the wrong mode. Professional meters can be returned to the manufacturer for calibration.

Common mistakes when reading an EMF detector

• Comparing an RF number with a magnetic field number. They measure different things.
• Holding the meter against your body or with fingers over the sensor.
• Taking one quick reading and treating it as a fixed level.
• Forgetting your own phone is on and transmitting in your pocket.
• Mixing up mG and µT, which are a factor of 10 apart.

Which meter suits your readings?

If your main concern is Wi-Fi, phones and masts, an RF meter such as the Safe and Sound Pro II RF Meter shows power density with peak and average modes. For wiring, appliances and power lines, a low-frequency meter such as the ME3030B ELF Tester measures magnetic and electric fields at 50 Hz. Browse every option in our EMF detectors collection.

Frequently asked questions

What is a good EMF reading?

There's no universal "good" number. Compare against a quiet spot in your own home and against international guideline levels, then set a target that suits you.

What does mG mean on an EMF meter?

Milligauss, a unit of magnetic field strength. 10 mG equals 1 µT.

Why does my EMF reading keep jumping?

Wi-Fi, Bluetooth and mobile signals are pulsed, so peak readings flicker. Use average mode or watch the maximum hold value instead.

Can I use my phone as an EMF meter?

Phone apps mostly read the phone's magnetometer, which isn't designed to measure RF or 50 Hz fields accurately. A dedicated meter is far more reliable.

Start with a baseline

Misuratore RF ricaricabile Safe and Sound Pro II 200 MHz – 8 GHz

The most useful reading you'll ever take is the first one: a calm, logged survey of each room before you change anything. Choose a meter that matches the fields you care about from our EMF detectors, or contact our team for help picking one.

This guide is general information about measuring equipment. EMF meters report field levels; they are not medical devices.