Stud Finder
How Does a Magnetic Stud Finder Work?
Magnetic stud finders are passive devices. They rely on the physical principle that magnetic materials attract. Neodymium magnets (rare-earth magnets) are extremely powerful and can detect the magnetic fields of steel screws through thick drywall. A smartphone-based magnetic stud finder takes this a step further by utilizing the built-in 3D magnetometer sensor. It digitizes the magnetic flux density, allowing you to see the exact signal rise on a real-time graph, rather than relying on feeling a physical pull. Our app samples the sensor at 50 Hz, and the full signal chain is described in our explainer on how magnetometer sensors work. The one hardware prerequisite is the sensor itself: about 14% of Android devices do not have a magnetometer, which is why whether a phone can be used as a stud finder starts with a free compatibility check.
How Does an Electronic Stud Finder Work?
Electronic stud finders are active sensors. They contain capacitive plates that project an electrostatic field into the wall. As you slide the device, it measures changes in the dielectric constant (relative density) of the material. A higher density indicates a solid object behind the drywall, such as a wood stud. Modern multi-scanners use multiple frequencies to estimate depth and try to filter out pipes and electrical wiring. That filtering is imperfect, and it collapses entirely on the wall types covered in our guide to stud finders failing on exterior walls.
Which Is More Accurate: Magnetic or Electronic?
Each tool has distinct trade-offs. Magnetic finders (and phone apps) are highly reliable, require no complex calibration, and have zero false positives for non-metal objects (like wiring or plumbing). However, they only locate fasteners, not the wood itself. Electronic finders can find the edge of wood directly, but they require batteries, constant calibration, and are notorious for giving false positives on wiring, damp insulation, or pipes. Magnetic tools have their own failure mode, and it is worth stating plainly: they respond to any ferrous metal, so drywall corner bead, an outlet box, a steel nail plate or a run of steel conduit will all register. Neither type can be trusted as a wire detector, which is why the safe-drilling rules matter regardless of which tool you own.
Which Stud Finder Should You Use for Drywall, Plaster or Metal Studs?
For standard 1/2-inch drywall, both tools work, though magnetic finders are often faster and cheaper. For historic plaster and lath walls, electronic finders fail completely; magnetic tools are your only viable option. For plaster over steel wire lath, neither tool works, because the mesh saturates a magnetic sensor across the whole wall — the detail is set out in our plaster and lath guide. For metal studs, a magnetic sensor will tell you clearly that the framing is steel, because the whole channel is ferromagnetic and produces a continuous band rather than discrete spikes; what it will not give you is a precise stud centre, so treat it as a material test rather than a location tool and read how to work with metal studs. On standard drywall over wood studs, which is the case the Stud Finder app is designed for, the magnetic approach is both the simplest and the most dependable.