Quick Answer: There’s no single depth spec, and no manufacturer publishes one, because coil size, frequency, target size, and soil mineralization all move detection depth independently. Garrett’s own published example is one of the few real numbers you’ll find: a 4-inch coil locates a quarter-sized coin around 4 inches down, a 12-inch coil finds the same coin around 12 inches down. In average soil, most consumer VLF machines find coin-sized targets in roughly the 6-10 inch range; in heavily mineralized “hot ground,” a pulse-induction machine like the Minelab GPX 6000 holds its depth where VLF machines lose signal, because PI ignores ground mineralization almost entirely. More depth is usually a coil or ground-balance question, not a “buy a new detector” question.
Every detector listing on Amazon implies a depth number somewhere in its marketing, and almost none of them come from the manufacturer. We went back to what Garrett, Minelab, and Nokta actually publish — not forum folklore — to explain what really decides how deep your machine reaches, and which machines in our own rankings are actually built for it.
Why there’s no single “detection depth” spec
Ask five manufacturers for a maximum detection depth and you’ll get five different non-answers, because depth isn’t a fixed property of a detector — it’s the output of four variables working together, and any one of them can add or subtract most of your depth on its own. A coin at 4 inches in clean dry soil and the same coin at 4 inches in iron-rich clay are two completely different targets to the same machine. That’s why our coin detecting guide found that no manufacturer — not Garrett, not Minelab, not Nokta — publishes a typical burial depth for a US coin. The “top six inches” figure repeated across detecting forums traces to hobbyist folklore, not to a spec sheet.
The four variables that actually decide depth
| Variable | More depth when... | Less depth when... |
|---|---|---|
| Frequency | Lower kHz, larger/conductive target (silver, large relics) | Higher kHz favors small/low-conductivity targets (gold) but loses raw depth |
| Coil size | Bigger coil pushes more signal into the ground | Small coil trades depth for target separation |
| Target size & orientation | Large targets, flat-facing the coil | Small targets, edge-on to the coil (a ring standing on edge reads far shallower) |
| Soil mineralization | Clean, dry, low-mineral soil | Iron-rich "hot ground," wet salt sand, black sand |
Frequency is the trade-off every buyer eventually runs into. Our silver detecting guide covers the low end of this scale: old silver coins read as large, highly conductive targets, so a lower frequency (4-5 kHz) favors them at depth. Our gold detecting guide covers the opposite end — gold flakes and small nuggets are small, low-conductivity targets, so dedicated gold machines run 45-71 kHz instead, trading raw depth for sensitivity to targets a low-frequency machine would miss entirely. Simultaneous multi-frequency machines like the Minelab Equinox line sidestep the trade-off by transmitting several frequencies at once, which is the main reason they dominate our overall rankings.
Coil size is the variable Garrett actually puts a number on: “a 4-inch coil might locate a standard-size coin, like a quarter, at a depth of 4 inches, while a 12-inch coil could find the same coin at a 12-inch depth.” A bigger coil isn’t a strictly better coil, though — it also covers more ground per sweep, so it hears more targets at once, which is exactly the problem a smaller coil solves in a trashy park.
VLF vs. pulse induction: the real depth divide
The biggest depth gap in the hobby isn’t between a $300 machine and a $1,000 machine — it’s between VLF (very low frequency) technology and pulse induction (PI). Every detector in our main rankings except dedicated prospecting machines is VLF, and VLF detectors read a mineralized ground’s background signal as noise, which forces them to reduce sensitivity to filter it out. Pulse-induction machines, like the Minelab GPX 6000 covered in our gold guide, work on a different principle entirely — they ignore ground mineralization almost completely, so they hold their full depth in black sand and iron-rich clay where a VLF machine is already fighting for signal. The catch is real: PI machines give up fine target ID (most can’t tell a nail from a nugget), weigh more, and cost far more — the GPX 6000 runs $5,999. That trade only makes sense once you already know your ground is both mineralized and worth digging.
Minelab Equinox 900 — Best All-Around Depth
- Multi-IQ simultaneous multi-frequency (4-40 kHz) — no single-frequency trade-off between depth and target type.
- Eight levels of adjustable recovery speed for separating deep, tightly packed targets.
- Ships with two coils (6" EQX06 and 11" EQX11) so you can trade depth for separation on the fly.
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Minelab Manticore — Best Raw Power
- Roughly 50% more transmit power than the Equinox line, per Minelab — real depth on deep, old targets.
- 2D target-ID map separates good targets from iron falsing that would otherwise mask a deep signal.
- Waterproof to 5 m, current flagship of the hobby.
Garrett AT Pro — Best Ground Balance at Mid-Range
- Manual ground balance for cancelling hot-ground signal that eats into VLF depth.
- 40 iron discrimination levels — fine-tune rejection instead of losing depth to blanket discrimination.
- Submersible to 3 m; a genuine published Garrett waterproof rating.
Nokta Legend 2 — Best Selectable Low-Frequency Mode
- Selectable single frequencies down to 4 kHz for maximum depth on large, conductive targets like silver.
- FerroCheck gives a direct ferrous/non-ferrous readout on deep, ambiguous signals.
- Waterproof to 5 m; 6,700 mAh battery for full-day depth-hunting sessions.
What actually improves your real-world depth
Buying a new detector is rarely the fastest way to hunt deeper. In order of actual impact:
- Ground balance it properly. A poorly balanced machine loses real depth to hot-ground noise long before it loses depth to its frequency or coil spec. Manual ground balance (Garrett AT Pro) or tracking ground balance (Minelab Equinox) both beat a fixed-balance budget machine in mineralized soil.
- Size up your coil if your sites are open and clean — the single biggest depth upgrade available on most machines, and usually cheaper than a whole new detector.
- Slow your sweep speed. Fast sweeping is the most common way hobbyists quietly lose depth; the coil needs time over a target to process a deep, weak signal correctly.
- Dig your trash. A machine ground-balanced and run in a site still littered with modern junk reads shallower effectively, because every false signal costs you time you could spend covering ground that hasn’t been hunted.
The bottom line
Detection depth isn’t a spec you can compare on a box — it’s the product of frequency, coil size, target size, and soil mineralization working together, which is exactly why no manufacturer will put a single number on it. For most all-around depth, the Minelab Equinox 900 ($999) is the machine to beat. Chasing depth specifically in mineralized ground, step up to the Manticore ($1,699) or, for serious gold prospecting in hot ground, the pulse-induction machines in our gold detector guide. Hunting old silver instead, where low frequency is the real depth lever? Our best metal detector for silver guide ranks the field by exactly that spec. And if your actual problem is a hunted-out park rather than raw depth, our coin detecting guide explains why target ID resolution — not depth — is usually the fix.