Which EMF Meter Do You Need? RF vs Low-Frequency Explained

The EMF meter you need depends on what you want to measure. Wi-Fi, phones, masts and smart meters need a radiofrequency (RF) meter. Wiring, consumer units and appliances need a low-frequency meter. The two measure different things, and buying the wrong one is the most common mistake: you'll get a reading of nearly zero next to the very thing you were worried about. This guide explains the difference and helps you pick.

Why can't one meter measure everything?

"EMF" covers several different things. Wireless devices send out radio waves at millions or billions of cycles per second. Mains electricity in the UK alternates at 50 cycles per second. These are so far apart that measuring them needs completely different sensors.

That's why an RF meter held next to your consumer unit reads almost nothing, and a low-frequency meter held next to your router reads almost nothing. Neither meter is broken. Each is simply built for a different job.

What does an RF meter measure?

An RF meter measures radiofrequency signals from wireless sources, including:

• Wi-Fi routers and extenders
• Mobile phones and masts, including 4G and 5G
• Smart meters
• Cordless phones, baby monitors and Bluetooth devices

Readings are shown in volts per metre (V/m) or microwatts per square metre (µW/m²). Check the meter's frequency range: to cover UK Wi-Fi and most 5G, you want a range reaching at least 6GHz. Millimetre-wave 5G, at 26GHz and above, needs a specialist meter.

What does a low-frequency meter measure?

A low-frequency meter measures the fields around mains electricity, including:

• House wiring, especially behind walls and under floors
• Consumer units and electricity meters
• Appliances, chargers and extension leads
• Overhead lines and substations

These fields come in two kinds, and some meters measure both:

• Magnetic fields, in milligauss (mG) or microtesla (µT), produced when current flows
• Electric fields, in volts per metre (V/m), present whenever something is plugged in, even if it's switched off

Which do you need?

If you're not sure, start with RF. Wireless sources are what most people are curious about in the first place.

What does calibration mean, and why does a certificate matter?

Calibration means the meter has been checked against a known reference, so the number on its display matches a real physical quantity.

Without calibration, you can compare one reading with another from the same meter, but you can't trust how either compares with published figures. If you plan to make decisions based on your readings, such as whether to buy shielding, calibration matters.

We're an authorised distributor for Safe and Sound meters and supply them with calibration certificates.

Safe and Sound meters: which one for which job?

• Safe and Sound Pro II — the one most people doing a whole-house RF survey choose. Detailed readings and suitable for methodical, room-by-room surveys.
• Safe and Sound Classic III — a simpler RF meter for quick checks. A good choice if you mainly want to know whether a reading is low, moderate or high.
• Safe and Sound Micro — a small wearable RF monitor for keeping an eye on levels as you move around, rather than for detailed surveys.

These Safe and Sound models are RF meters. For wiring and appliances, you need a low-frequency meter as well. You can compare everything we stock on our EMF detectors page, and each product page states the meter's frequency range.

What will you regret buying?

• A phone app. Apps use your phone's compass sensor, which can't measure radiofrequency at all.
• An RF meter to check your wiring, or a low-frequency meter to check your Wi-Fi.
• A cheap "3-in-1" meter without clear specifications. If it doesn't state its frequency range and accuracy, its readings are hard to rely on.
• An RF meter that stops below 6GHz, if 5G or 5GHz Wi-Fi is what you want to check.

Once you have a meter, what next?

Our step-by-step guide to finding EMF hotspots in your home shows you how to take readings you can repeat, and what to do with the results.

Frequently asked questions

What's the difference between an EMF meter and an RF meter?

"EMF meter" is a general term. An RF meter is one type, measuring wireless signals. A low-frequency meter is another, measuring fields from wiring and appliances. You need the type that matches what you want to check.

Can one meter measure Wi-Fi and wiring?

Some combination meters claim to, but they often compromise on one side. For reliable readings of both, most people use a dedicated RF meter and a dedicated low-frequency meter.

Which EMF meter is best for 5G?

For most UK 5G, which runs around 3.5GHz, an RF meter reaching at least 6GHz. Millimetre-wave 5G at 26GHz and above needs a specialist meter.

Do EMF phone apps work?

No. They read the phone's compass sensor, which can't detect radiofrequency and isn't calibrated for low-frequency fields.

Does an EMF meter need calibrating?

If you want to compare readings with published figures or make decisions based on them, yes. A calibration certificate confirms the display matches a real measurement.

This article explains how different EMF meters work and which to choose. It does not make health claims. UK and international health bodies do not consider harm to be established at exposure levels below international guidelines.