On a coin-sized target in ordinary soil, an entry-level detector recovers roughly 6 to 10 inches. The two-to-three-foot figures on packaging refer to large objects such as pipes or manhole covers, in ideal ground.
Depth is the most advertised and least useful number in detecting. It is quoted for the best case and experienced in the average one, and the gap between them is where a lot of buyer disappointment lives.
Why target size changes everything
A detector sees a target's surface area, not its value. A coin is small, so its signal is weak and fades quickly with depth. A large iron pipe returns a signal from far deeper. Both numbers are true; only one of them is about the thing you are hunting.
What actually reduces your depth
| Factor | Effect |
|---|---|
| Mineralised or red soil | Substantial loss - often several inches |
| Wet salty sand | Substantial loss on single-frequency machines |
| Small or thin target | Substantial loss |
| Target on edge rather than flat | Substantial loss |
| Nearby iron trash | Masks the target entirely |
| Larger coil | Gains depth on big targets, loses small ones in trash |
| Sensitivity turned down for stability | Small loss, usually worth it |
Coil size is a trade, not an upgrade
A bigger coil covers more ground and reaches deeper on larger targets, but it separates poorly in trash and can miss small objects sitting between junk. In a rubbish-filled park a smaller coil frequently finds more, despite being the shallower choice on paper.
Multi-frequency and difficult ground
The main practical benefit of multi-frequency machines is not raw depth in clean soil - it is holding onto depth where single-frequency machines lose it, particularly wet sand and mineralised ground. That is the real reason it is worth having at entry level now that it exists there.
How we measure it, and why
We bury the same five targets at 4, 6 and 8 inches and record what each machine actually calls, rather than repeating manufacturer figures. A detector that reports a clear, correct ID on a dime at 6 inches is more useful than one that gives a vague blip at 9 - because you will dig the first and walk past the second.
That is the number in the depth score in our ranking, and it is why the order there does not match the order of the depth claims on the boxes.