How to Plan a Gravel Driveway: Layers, Depths and How Much to Order

By the SAA Tool editor, an IT support engineer · Last reviewed 9 October 2026 · 7 min read

A gravel driveway is a small road, and it lasts for the same reasons: it's built in compacted layers on ground that drains. This guide covers each layer's job, published depths from the US and UK, why you order more loose stone than the finished volume, and the sums in feet and metres. It's general information for planning. Soft or wet ground, slopes and heavy vehicles need a local contractor or engineer who can see the site, and access and planning rules come from your local authority.

Why driveways are built in layers

Each compacted layer spreads the load from a tyre over a wider area, so the soil underneath is pressed less hard and doesn't rut. Layers also put the right stone in the right place. The US Gravel Roads Maintenance and Design Manual explains that good base gravel has larger stone and little fine material, so it's strong but "will not form a crust", while good surface gravel needs stone for strength, sand to fill the gaps and some fines, often clay, to bind it.

Layer	What it does	Typical material
Subgrade	The ground it all sits on, cleared of turf and roots and compacted	Existing soil, often under a geotextile fabric
Sub-base	Spreads the load; on permeable designs, lets water drain through	Larger crushed stone
Base	A dense, level platform for the surface	Graded crushed stone, such as 3/4 in (19 mm) maximum size
Top	The surface: binds, sheds water and looks right	Finer crushed stone with fines, or decorative gravel

The UK guidance below says the geotextile stops the sub-base sinking into the soil and helps keep weeds down.

How deep? Three published examples

Who publishes it	What it asks for
Union County Engineer, Ohio, US: residential driveway minimums	8 in (20 cm) of crushed aggregate, or 2 in of asphalt over 6 in of aggregate. Minimum width 10 ft (3.05 m).
Metropolitan Water District of Salt Lake & Sandy, Utah, US: gravel roads or driveways	A compacted subgrade, a 4 in (10 cm) base course compacted to 95% of maximum density, then a 2 in (5 cm) top course of 3/4 in minus gravel or crushed rock.
UK government guidance on permeable front gardens (England)	A geotextile over the soil, about 150 mm (6 in) of compacted sub-base, and roughly 200 to 250 mm (8 to 10 in) of construction in all.

So published figures run from about 6 to 10 in (15 to 25 cm) of stone. Each reflects its own ground, climate and traffic. The UK guidance includes a quick soil check: if it's hard to drive a 50 mm (2 in) square wooden peg more than 150 mm (6 in) into the ground, the soil is strong enough; if the peg goes in easily, "the ground may be too soft and you will need expert advice". Wet or clay ground, slopes and heavy vehicles need a local professional too.

Compaction: why you order more than the finished volume

Rolling, rain and traffic push loose stones together, so a layer ends up thinner. The gravel roads manual says ordinary compaction makes most gravels shrink by at least 20%, and that in many areas the drop is 30% or more. It warns against working out quantities from the volume in the truck or stockpile, because stockpiled material "is very loose and has very low density".

The shrink isn't the extra you order. Divide the finished volume by the share that's left:

Expected shrink	Extra needed	Calculator option
15%	1 ÷ 0.85 = 1.18, so 18%	20%
20%	1 ÷ 0.80 = 1.25, so 25%	25%
25%	1 ÷ 0.75 = 1.33, so 33%	35%
30%	1 ÷ 0.70 = 1.43, so 43%	45%

Our Driveway Gravel Calculator adds 25% by default, which covers the manual's minimum 20% shrink, and offers None or 10% to 45% in steps of 5%. The real shrink depends on the stone and how well it's compacted, so any percentage is an estimate. Ask your supplier what to expect and pick the option from the table, rounding up.

Weight doesn't shrink. If your supplier quotes a compacted weight per cubic yard or m³, multiply it by the finished volume and add only a little for waste. If the figure is for loose stone, or you're not sure, add the full allowance.

Drainage and crown

The manual calls standing water a major cause of failure on gravel roads, and recommends a crown, with the middle higher than the edges, of about ½ inch per foot, roughly 4%. Too little and water sits on the surface, softens it and forms potholes; too much and vehicles tend to slide towards the edge. On a 10 ft drive crowned in the middle, ½ in per foot over 5 ft puts the centre about 2.5 in above the edges; on a 3 m drive, 4% over 1.5 m gives 6 cm.

UK guidance: slope the drive away from the house and towards the road where possible, don't send water towards a neighbour, and a drive steeper than 1 in 20 (5%) may not suit permeable surfacing. On clay soils, a connection to the drains may be needed.
Union County, Ohio: where the road has no kerb, the drive must slope down and away from the road edge for at least 4 ft (1.2 m), and no steeper than 10% beyond that.

Permissions differ too. Union County requires a driveway permit before work starts. In England, a permeable front drive, such as gravel, needs no planning permission whatever its size, but crossing a pavement needs the council's permission to drop the kerb.

Worked example in imperial and metric

Imperial: a 60 × 10 ft drive (600 sq ft) with a 4 in sub-base, 2 in base and 2 in top layer. Metric: an 18 × 3 m drive (54 m²) with 24 cm of stone, split 15, 5 and 4 cm. Both use dry gravel at 1,680 kg/m³ (1.42 US tons per cubic yard) and the default 25% extra; the splits are only illustrations.

Layer	Imperial: finished, then to order	Metric: finished, then to order
Sub-base	600 × 4 ÷ 12 = 200 cu ft = 7.41 cu yd; order 9.26 cu yd (13.11 US tons)	54 × 0.15 = 8.1 m³; order 10.13 m³ (17.01 tonnes)
Base	100 cu ft = 3.70 cu yd; order 4.63 cu yd (6.55 US tons)	54 × 0.05 = 2.7 m³; order 3.38 m³ (5.67 tonnes)
Top	100 cu ft = 3.70 cu yd; order 4.63 cu yd (6.55 US tons)	54 × 0.04 = 2.16 m³; order 2.70 m³ (4.54 tonnes)
Total	14.81 cu yd; order 18.52 cu yd (26.22 US tons)	12.96 m³; order 16.20 m³ (27.22 tonnes)

Rows are rounded, so they may not add up exactly. If your supplier expects a 30% shrink, choose 45%: 21.48 cu yd (30.41 US tons) or 18.79 m³ (31.57 tonnes).

Using the Driveway Gravel Calculator

Open the Driveway Gravel Calculator and choose Units and the Material. If your supplier gave a weight, choose My supplier’s figure and type it into Weight of the material, in tons per cubic yard or tonnes per m³.
Enter the Driveway length and Driveway width.
Under Layers (finished depth, after compacting), fill in Sub-base, bottom (optional), Base, middle and Top layer in inches or centimetres. Enter 0 for a layer you don't need.
Pick the Extra for compaction and spreading: None, or 10% to 45% in steps of 5%. The default is 25%.
Press Calculate (results also update as you type). You get the total to order in cubic yards, cubic metres and US tons or tonnes, and an Each layer table. Reset restores the defaults.

Two limits. It works on a rectangle, so work out a turning area or wider entrance separately and add it. And it uses one material weight for every layer, so if your sub-base and top stone weigh differently, run it once per layer with 0 in the others. The Gravel Calculator handles circles, the Area Converter handles square yards or acres, and How much gravel do I need? explains the conversions.

Planning checklist

Check local rules: driveway or access permits, dropped kerbs, planning, minimum widths and drainage.
Test the ground, and get professional advice for soft or wet ground, slopes and heavy vehicles.
Agree the layers and finished depths with your contractor or the local standard.
Plan where water goes: a crown or cross slope, draining away from the house and neighbours.
Ask the supplier whether they sell by weight or volume, what each stone weighs per cubic yard or m³ (loose or compacted) and how much it compacts.
Order each layer with a compaction allowance, then spread and compact each one before the next goes on.
Plan the edges: the UK guidance suggests a strip of paving or asphalt at the entrance to limit gravel spreading.

Sources

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