Gravel calculator

How to calculate how much gravel you need

Measure the area in m², multiply by the depth in metres, then by the stone's density in tonnes per m³, and add about 10% for uneven ground and settling. An 8m × 4m drive is 32m². At 50mm deep that is 1.6m³, which at 1.6 tonnes per m³ is 2.56 tonnes, or 2.82 with waste: 4 bulk bags or a 3-tonne loose load.

Density matters because stone types weigh different amounts. Slate and Cotswold chippings are lighter than granite or basalt, so the same area needs fewer tonnes. The calculator shows the density it uses for each stone, and you can change it to your supplier's figure.

How much does a tonne of gravel cover?

A tonne of 20mm gravel covers 12.5m² at 50mm and 15.6m² at 40mm. Lighter stone goes further, heavier stone less far.

How much does a bulk bag of gravel cover?

An 800kg bag of 20mm gravel covers about 10m² at 50mm. Bags are not all the same weight: the suppliers checked sell 800kg bags, some sell heavier ones, and a bag sold as a "tonne bag" often holds less than a tonne. Go by the weight printed on it, and put that weight into the calculator.

How many 25kg bags of gravel per m²?

3.2 bags per m² at 50mm, and 2.6 at 40mm, for 20mm gravel. Small bags are handy for topping up a border, but on anything bigger a bulk bag or a loose load costs much less per tonne.

How deep should gravel be?

Deep enough to cover the ground without being so deep that you sink into it. Decorative Aggregates puts 10mm stone at 30 to 40mm in borders but at least 50mm on a drive, and IBRAN warns that small stone sticks in tyres, so 20mm angular is the usual choice for drives.

How much gravel do I need for a driveway?

A gravel drive is a build-up, not just stone. For the 8m × 4m example, with the 4m end against the house:

• Dig out 200mm: 6.4m³ of soil, about 2 × 6-yard skips by volume.
• Weed membrane on the ground: 35.2m² with overlaps.
• MOT Type 1 sub-base at 150mm compacted: 11.1 tonnes with waste.
• 20mm angular gravel at 50mm: 2.82 tonnes with waste.
• Edging along the three open sides: 20m.

Is 2 inches of gravel enough for a driveway? For the top layer, yes: 50mm is the usual depth. It is not enough on its own. Without a compacted sub-base under it, the stone is pushed into the soil and the drive ruts.

Should I use 10mm or 20mm gravel for a driveway?

20mm angular gravel: IBRAN calls it the best choice for a drive, and angular stone locks together where round stone rolls. Small stone sticks in tyre treads and gets carried into the house, so 10mm and pea gravel suit paths and borders better.

Can I just put gravel over dirt?

On a path or a border you can lay it over firm, weeded ground with a membrane. For a drive, no: the stone sinks into the soil, weeds come through, and the surface ruts. A drive needs dug-out ground, a membrane and a compacted MOT Type 1 sub-base first. Under a raised deck, a membrane with a layer of gravel keeps the weeds down: the decking calculator does the deck itself.

MOT Type 1: how much sub-base do I need?

Type 1 is crushed stone that compacts into a solid base. It is ordered by its compacted weight: this calculator uses 2.1 tonnes per compacted m³, so a tonne covers 4.8m² at 100mm and 3.2m² at 150mm. That is a little more than Pavingexpert's 5m² and 3.5m², so you are not left short. Use 150mm under a drive and 75 to 100mm under a path or patio. For the sub-base on its own, use the MOT Type 1 calculator.

Self-binding gravel

Self-binding gravel has fine material in it that sets hard when it is watered and rolled, so it does not move about like loose stone. Breedon lays it at 50mm compacted and no thicker, straight onto Type 1, and says a tonne covers about 8m². It does not drain through, so it needs a fall: 1 in 40 on a drive and 1 in 50 on a path. A membrane, if you use one, goes under the Type 1, not under the gravel.

Gravel grids

A gravel grid is a plastic honeycomb that holds the stone in place, so it does not drift or rut. It sits on the sub-base, and the gravel fills the cells and about 10mm over the top. With 500 × 500mm panels, a 32m² drive takes 128 panels, 135 with 5% spare, filled to 50mm in a 40mm grid. Worth it on a slope, a drive with a lot of turning, or where loose stone would spread onto a pavement.

Loose load, bulk bags or 25kg bags?

A loose load from a tipper is usually the cheapest per tonne on a bigger job, but it is tipped where the lorry can reach, so it needs space. Bulk bags are lifted off by crane, need clear access, and can sit on the drive until you use them. 25kg bags are easy to carry but the most expensive way to buy anything more than a top-up.

Do I need planning permission for a gravel driveway?

Government guidance for England says hard surfacing more than 5m² of a front garden is permitted development only where the surface is permeable. Loose gravel over a permeable sub-base lets water through, so it usually needs no planning permission. A dropped kerb is separate: ask your council.

How much does a gravel driveway cost?

Howmuchgravel's 2026 guide puts 20mm gravel at £35 to £70 a tonne depending on type, MOT Type 1 at £25 to £40 a tonne, membrane at £1 to £2 per m², a 6-yard skip at £200 to £350 and labour at £25 to £45 per m². All in, that comes to about £25 to £51 per m² done yourself, or £49 to £92 per m² fitted. These are estimates: prices vary by region and stone.