Gravel Calculator — How Much Gravel Do I Need?

For a driveway, gravel should be laid at least 100mm (4 inches) deep on top of a compacted Type 1 sub-base. Use our Type 1 Sub-Base Calculator to work out sub-base quantities. Decorative driveways may use 50mm of decorative gravel over 100-150mm of sub-base. Without adequate depth, gravel will shift under vehicle weight and develop ruts.

Gravel weight varies by type: loose decorative gravel is typically 1.5 tonnes per m³, pea gravel around 1.6 tonnes per m³, and driveway-grade angular gravel (20mm) around 1.8 tonnes per m³ once compacted (loose, it is closer to 1.6-1.7). Slate chippings are lighter at roughly 1.4 tonnes per m³, as slate is a flat, low-bulk-density stone. This gravel tonnage calculator uses the appropriate density for your chosen gravel type, and you can override it in the advanced options if your supplier quotes a different figure.

Angular 20mm gravel (also called driveway aggregate or driveway shingle) is the most popular choice for UK driveways as it locks together under compaction. Golden gravel, cotswold stone, and granite chippings are all popular. Always lay gravel over a proper Type 1 MOT sub-base with a geotextile membrane to prevent mixing with the subsoil.

Decorative gravel for garden paths and borders should be 30-50mm deep. At 50mm depth, you get good coverage that stays in place and suppresses weeds. Always use a weed membrane underneath. For a solid paved surface instead, see our Paving Slab Calculator.

Yes. Divide the L-shape into two rectangles, run the calculator for each one and add the results. Gravel is a loose material, so volumes and tonnages from the separate sections are simply additive: the summed figure is exact, with no cutting waste where the sections join (unlike paving or decking boards). Each section can have its own depth if, say, a parking area needs 100mm but a garden path only 50mm. When ordering bulk bags, add the volume or tonnage totals first and convert to bags once at the end, since each run rounds its bag count up and adding rounded counts can cost you an extra bag.

A standard UK bulk bag (also called a dumpy, jumbo or tonne bag) holds roughly 800-850kg of gravel, which is about 0.5-0.566 m³ — not a full cubic metre. For a typical single-car driveway (3m x 6m at 100mm deep), the bare volume is 1.8 m³, which already needs about 4 bulk bags (1.8 ÷ 0.566 = 3.18, rounded up); adding the recommended 10% wastage gives 1.98 m³, still 4 bulk bags. This gravel quantity calculator works this out automatically using a 0.566 m³ bag by default, which you can change. For French drain gravel, see our French Drain Calculator.

Gravel density in kg per m³ is the same set of figures this calculator uses internally, just expressed in kilograms instead of tonnes: decorative gravel (10-20mm) is 1,500 kg/m³, pea gravel (10mm) is 1,600 kg/m³, driveway-grade angular 20mm gravel is 1,800 kg/m³ compacted, and slate chippings (20-40mm) are 1,400 kg/m³. To convert, 1,000 kg/m³ equals 1 tonne per m³, the unit this calculator's results are shown in. For sand, ballast, Type 1 MOT and other materials with their own densities, see our Aggregate Calculator.

Small retail bags of gravel are usually sold at 25kg (sometimes 20kg) for top-ups and small jobs, unlike the roughly 800-850kg bulk bags this calculator's bag count is based on. Using this calculator's own density figures: a 25kg bag of decorative gravel (1.5 tonnes/m³) works out to 25 ÷ 1,500 = 0.0167 m³ per bag, covering about 0.0167 ÷ 0.05 = 0.33 m² at the typical 50mm decorative depth, so 1 m² needs roughly 3 bags. For driveway-grade 20mm gravel (1.8 tonnes/m³) at the typical 100mm driveway depth, a 25kg bag covers 25 ÷ 1,800 ÷ 0.1 = about 0.14 m², so 1 m² needs roughly 8 bags (7.2 rounded up). If your bags are 20kg rather than 25kg, scale the coverage down by 20/25 (0.8 times). Bulk bags work out far cheaper per tonne than small bags for anything beyond a border or top-up.

Coverage from 1 tonne depends on the gravel's density and how deep it is laid, using the same volume-over-depth arithmetic this calculator performs. At a typical 50mm decorative depth: 1 tonne of decorative gravel (1.5 tonnes/m³) gives 1 ÷ 1.5 = 0.667 m³, covering 0.667 ÷ 0.05 = about 13.3 m². Pea gravel (1.6 tonnes/m³) covers about 12.5 m² at 50mm, and slate chippings (1.4 tonnes/m³) about 14.3 m² at 50mm, since a lighter material stretches further for the same weight. At the deeper 100mm typical driveway depth, 1 tonne of driveway-grade 20mm gravel (1.8 tonnes/m³) gives 1 ÷ 1.8 = 0.556 m³, covering about 5.6 m². UK aggregate suppliers price and deliver by the metric tonne (1,000kg); the older imperial 'ton' is rarely used in the trade today, so the two terms are generally treated as interchangeable in supplier price lists.