Detection depth is stated per material, never as one number
Manufacturers publish detection depth per material — one figure for wood, another for non-magnetic metal, another for live cable — because the physics differs in each case. A single headline depth on the box is the deepest of them, not the one that applies to the joist you are looking for. Damp plaster and foil-backed board both change what the tool sees. We compare stated depth by material, the modes offered, how the tool calibrates when placed on the wall, and marking aids.
Wood 19 mm (0.75 in) · metal 30 mm (1.18 in) · deep 38 mm (1.50 in) · live cable 50 mm (1.97 in) at 230 V
The only detector here that publishes a depth for every material it claims: wood to 19 mm (0.75 in), metal to 30 mm (1.18 in), deep scan to 38 mm (1.50 in) and live cable to 50 mm (1.97 in) at 230 V.
Best for: Anyone who wants to know what the depth figure means before trusting it.
Metal, live cable and timber · three-color LED ring · center indication · IP54
A site-rated scanner that identifies which material it has found and rings the marking hole with a three-color LED — red on the object, yellow approaching, in an IP54 rubber housing.
Best for: Repeated drilling on site, where finding the center of the stud quickly matters more than reading a depth.
≈ $99
Five detection modes · wood, metal and AC cable · works through several wall finishes
A five-mode wall scanner covering wood, metal and live AC cables, stated to work on lath, wallpaper, wooden floors, acoustic ceilings and painted walls.
Best for: General household scanning where the question is "is there anything there" rather than "how deep".
Transmitter plus receiver · up to 2 m (7 ft) reception depth · 7 channels · live and dead cables
Not a wall scanner but a cable tracer: a transmitter injects a signal into a conductor and a receiver follows it, to a stated depth of 2 m (7 ft), on live or dead cables.
Best for: Following one specific cable through a building, which no wall scanner can do at all.
A detector that only sees timber lets cables and pipes through. The range of detection modes is what decides how safe the drilling is.
A simple detector locates a plasterboard stud, which is the most frequent need before fixing anything.
A detector limited to twenty millimeters sees nothing behind a forty-millimeter lining. The stated detection depth, per material, decides its usefulness on the wall you have.
No, never. It reduces the risk. Isolating the circuit concerned before drilling remains the only real safety measure.
Most units calibrate on an area assumed to be empty at start-up. Calibrating over a stud throws the whole search off.
Calibration done over an occupied area, a damp wall, or sensitivity set too high. Start the calibration again somewhere else.
The usable depth drops sharply in dense materials. Stated figures correspond to favorable conditions.
By sweeping in both directions to find both edges, and by checking the spacing is regular against the neighboring studs.
Metal detection modes sometimes see them; live voltage modes do not. That is a limit worth knowing.
Slow, attentive penetration leaves time to feel a change in resistance. It is one more precaution, not a guarantee.
Multifunction models flag a live conductor, not a dead buried cable. Before drilling, you switch the circuit off and assume a cable may run where you do not expect it.
No detector guarantees the absence of a cable: isolating the circuit before drilling remains the only real safety measure. Calibrate on an area assumed to be empty — calibrating over a stud throws the whole search off — and the stated depth collapses in concrete.
There is no table here, and the reason is in the listings. The figure published most often across these 4 products is measuring mode, given by 3 of them — short of the four in five a column needs to compare rather than to display gaps. Each product page says what its own maker published.
Specifications: manufacturer sheets for measuring instruments and the matching Amazon product pages. Prices and availability: Keepa.
Most recent revision in this category: August 31, 2026.
