How much gravel do I need? How to use the calculator
- 1Enter the length and width of the area, or the area itself.
- 2Enter the depth you want once it is laid.
- 3Choose the material; the typical density fills in.
- 4Enter the bag weight to see how many bags to order.
How to calculate gravel volume and weight (formula)
- 01Volume = area × depth × (1 + extra %)
- 02Weight = volume × density
- 03Bags = weight ÷ bag weight, rounded up
Suppliers often sell by weight (tonnes or tons) but you measure in volume, so density links the two. Typical values: gravel about 1.65 t/m³, sand 1.6 (damp sharp sand about 1.8), topsoil 1.3, bark mulch 0.35 — all vary with moisture.
Material that is compacted or firmed takes less room than it did in the lorry. A crushed-stone sub-base such as MOT Type 1 or crusher run shrinks by about 30 %, so the sub-base choice adds 35 % (30 % plus 5 % for levelling); loose topsoil firms from about 1.3 to 1.5 t/m³, so topsoil adds 15 %. The volume shown is what to order, loose.
Gravel calculation example
A 4 m × 3 m area at 50 mm deep, plus 5%, needs 0.63 m³ of gravel.
At 1.65 t/m³ that weighs 1.04 t — 2 bulk bags of 850 kg.
Tips before you buy
- Lay a weed membrane under decorative gravel.
- Check where a delivery lorry can tip or lift a bulk bag before you order.
- Choose "Sub-base to be compacted" for MOT Type 1 or crusher run under paving or a drive — it adds the 30 % that disappears when you compact it.
Frequently asked questions
How much does a cubic metre of gravel weigh?
About 1.5–1.8 tonnes, depending on the stone and how wet it is. We use 1.65 t/m³ unless you change it.
How many tons of gravel is a cubic yard?
Roughly 1.4 US tons for typical gravel.
How deep should decorative gravel be?
Usually 40–50 mm (about 2 in). Much deeper and it becomes hard to walk on.
How much MOT Type 1 do I need?
Area × compacted depth × about 1.3 for compaction, plus a little for levelling. For 12 m² at 100 mm: 1.2 m³ × 1.35 = 1.62 m³ of loose stone, about 2.6 tonnes. Pavingexpert's rule of thumb is about 1 tonne per 5 m² at 100 mm compacted.
Also searched as: crushed stone calculatorsand calculatortopsoil calculatorhow much gravel do I needaggregate calculator
Sources
- Typical bulk densities: aggregate supplier and engineering reference tables (values vary with moisture and grading).
- Pavingexpert – Sub-base: compaction of around 30 % with most Type 1 aggregates
- Marshalls – What sub-base do I need? (volume × 1.3 for compaction, × 1.6 t/m³)
- Mainland Aggregates – Sharp sand: approx 1.8 tonnes per cubic metre
- The Gardenmakers – bulk densities, loose and compacted (screened sandy loam 1.30 / 1.50 t/m³)
Formulas last reviewed: September 30, 2026 ·How we check our formulas