Measure Kit's magnetic field detector shows the magnetic field strength around your phone in microtesla (µT) with a live graph. It compares the reading with a slowly adapting baseline and beeps faster as the field rises above it, at low, medium or high sensitivity. It is included in Measure Kit Pro.
| Unit | Microtesla (µT); Earth's field is roughly 25-65 µT |
|---|---|
| Alert thresholds | About 45 (low), 25 (medium) and 12 µT (high) above baseline |
| Detects | Magnets and magnetic metals such as iron and steel |
| Cost | Included in Pro |
By Ship AI Lab. Last updated . Written from how the Measure Kit app actually behaves.
What the reading means
The number on screen is the strength of the magnetic field in microtesla (µT). Even with nothing nearby it is not zero, because the Earth's own field is typically somewhere between about 25 and 65 µT depending on where you are. Bringing the phone near a magnet or a piece of steel adds to that.
A graph keeps the recent history of the reading, so you can see a spike appear and fade as you sweep the phone along a surface.
An adaptive baseline, so alerts mean something
Measure Kit keeps a slowly moving baseline, an estimate of the ambient field around you. A spike means the reading rose above that baseline by more than a threshold. Because the baseline adapts slowly while a spike is active, holding the phone still over a piece of metal keeps the alert on instead of fading away.
Choose low, medium or high sensitivity. High reacts to a small rise of about 12 µT above baseline, medium to about 25 µT and low to about 45 µT. The stronger the field, the faster the beeps, and a haptic pulse goes with each one.
Resetting the baseline
If you walk into a new room or the baseline drifts, tap reset and the app takes the current reading as the new normal. Do this away from the thing you are looking for.
How to find magnets and steel
- Open the detector and hold the phone stillAway from other magnets, speakers and laptops for a few seconds so the baseline settles.
- Pick a sensitivityStart on medium. Use high for weak targets and low in cluttered places.
- Sweep slowlyMove the phone along the surface. The beeps speed up as the field rises.
- Save the peakSave the reading with a note in History to remember where you found it.
Practical uses
Finding fixings behind plasterboard
Steel screws and nails can show up as small spikes along a wall, though it is not a stud finder.
Is it really a magnet?
Test jewellery clasps, catches, toys and fridge magnets.
Locating a lost steel object
Keys or tools that fell behind furniture can react when you pass over them.
Science projects
Compare the field near different objects and graph how it changes with distance.
What it cannot do
- It only reacts to magnetic materials such as iron, steel, nickel and magnets. It will not find aluminium, copper, gold, silver or plastic.
- It is not a metal detector, an electrical safety tool or a health measurement. Do not use it to decide where it is safe to drill or cut near cables or pipes.
- The phone's own speaker and case magnets can influence the reading. Take the case off if it has a magnetic clasp.
Magnetic field detector questions, answered
Is the magnetic field detector free?
It is part of Measure Kit Pro, which also includes the AR tape measure, unlimited history and export.
What is µT?
Microtesla, a unit of magnetic field strength. The Earth's field is roughly 25 to 65 µT depending on where you are.
Can it find studs or pipes in a wall?
It may react to steel screws and nails, but it is not a stud finder and should not be trusted for safety decisions.
Why does the alert stop after a while?
The baseline adapts slowly to the new level. Hold still over the target to keep it on, or move away and back.
Will it find gold or aluminium?
No. It only detects magnetic materials.