Stud Finder: AI Metal Detector

Find hidden metal behind walls using your phone's magnetic sensor.

Stud Finder turns your iPhone's built-in magnetometer into a wall scanner and EMF meter. It detects ferrous metal (iron, steel) by measuring changes in the magnetic field in microteslas (µT): metal studs, the nails and screws that hold drywall to wood studs, steel pipes, rebar and other magnetic objects.

HOW IT WORKS
Your phone measures the magnetic field around it. When you open the app, a short guided calibration takes a baseline away from metal: you tilt the phone around a ring, and if metal nearby throws it off, the app tells you and starts over. After that, a rise over the baseline means there is metal close by. Slide the phone slowly across the wall: on a wood stud it beeps at each screw, and on a steel stud it beeps all along.

WHAT THE READINGS MEAN (above baseline)
- Empty wall: about the baseline (10–60 µT)
- Nail or screw: +5 to +20 µT
- Paper clip or washer: +20 to +50 µT
- Pipe or screwdriver: +50 to +100 µT
- Metal stud: +80 to +150 µT
- Strong magnet: +150 to 300+ µT

FEATURES
- Shows where your iPhone's sensor is, with a light at the edge of the screen that turns red over metal
- Guided calibration that checks you did it right
- Real-time µT reading
- Adjustable sensitivity
- Sound and vibration alerts
- Four-step tutorial
- Works without internet

TIPS FOR BETTER ACCURACY
- Take off the phone case before calibrating
- Calibrate away from walls, tables, appliances and laptops
- Pass the spot the app marks over the wall: on some iPhones it is at the top, on others at the bottom
- Beeps everywhere? Calibrate again near that wall, or lower the sensitivity

USE IT TO
- Locate studs behind drywall before hanging a shelf or a TV
- Find hidden screws, nails and steel pipes
- Measure magnetic fields around devices and magnets

Note: the magnetometer only reacts to magnetic (ferrous) metal. It does not see wood, plastic, copper or aluminum.