How Deep Should Gravel Be for a Driveway or Path?

Quick answer: For a driveway, lay gravel about 50mm (2in) deep as a top layer over a compacted sub-base of 100–150mm of MOT Type 1. For a garden path that only takes foot traffic, 40–50mm of gravel over a 50mm sub-base is enough. Loose gravel deeper than about 50mm just ruts and scatters — the depth belongs in the sub-base, not the surface.

Getting gravel depth right is what separates a firm, lasting surface from one that ruts, scatters, and shows bald patches. The instinct to pile it deep is usually wrong: firmness comes from a compacted base, not a thick layer of loose stone. This guide gives the correct depths for driveways and paths, explains why the sub-base matters more than the gravel on top, and shows how to calculate the two layers separately. Use the calculator above for your quantities.

Driveway depth

A gravel driveway is really two layers, and the depths differ. The sub-base is 100–150mm of compacted MOT Type 1 (crushed stone) — this is the load-bearing layer that stops the driveway rutting under a car’s weight. The gravel top layer is about 50mm (2in) of decorative or angular gravel laid over the sub-base.

The sub-base does the structural work; the gravel is the surface you see and hear. Skimp on the sub-base and no amount of top gravel will stop the driveway sinking and rutting — the loose stone just moves around on soft ground. For heavier use or poor ground, increase the sub-base toward 150mm rather than piling on more surface gravel.

Path depth

A path taking only foot traffic needs far less. Allow around 50mm of compacted hardcore or MOT Type 1 as a sub-base (on soft ground; firm ground may need less), with 40–50mm of gravel or shingle on top.

For a lightly used decorative path, you can sometimes lay gravel over a weed membrane on firm ground with a thinner base, but any path that gets real use benefits from a proper sub-base. The general principle is the same as a driveway, just scaled down: a modest compacted base does the work, and a shallow layer of gravel finishes the surface.

Why deeper gravel isn’t better

It’s tempting to lay a thick layer of loose gravel and skip the sub-base, but it doesn’t work. Loose gravel deeper than about 50mm ruts — tyres and feet push through it, creating channels and bald patches. It also scatters, migrating off the edges and needing constant raking back. And it wastes money, because you’re paying for depth that makes the surface worse, not better.

The firmness comes from a compacted sub-base, not a deep surface layer. Put the depth where it does the work: in the base. A thin, well-laid top layer over a solid base outperforms a thick layer of loose stone every time.

Edging keeps depth consistent

Gravel spreads sideways without a border. Edging — timber, metal, brick, or a mowing strip — holds the gravel in place, keeps the depth even, and stops it wandering into borders and lawns. Without edging, the gravel thins in the middle where it’s walked or driven and piles up at the edges, so you lose the consistent depth you laid. It’s a small addition that saves a lot of raking and topping up.

Calculating two layers

Because a driveway or path has two layers at different depths, you calculate each separately. Work out the sub-base as area × sub-base depth × its density (MOT Type 1 is denser than decorative gravel), then the gravel as area × 50mm × the gravel’s density. Then order both. They’re different materials at different depths, so a single figure won’t cover the job. The calculator lets you run each layer in turn — do the sub-base with MOT Type 1 selected, note the tonnage, then switch to your gravel and run the 50mm top layer.

Common mistakes to avoid

The biggest mistake is laying thick loose gravel with no sub-base, which ruts and sinks. Others include laying the surface gravel too deep (over 50mm loose gravel is unstable), skipping edging (so the depth becomes uneven), and calculating only the gravel while forgetting the sub-base is a separate, often larger, quantity. On soft or wet ground especially, the sub-base isn’t optional — it’s what keeps the whole surface from sinking.