How to calculate gravel in tonnes
Volume (m³) = length (m) × width (m) × depth (mm) ÷ 1,000
Tonnes = volume × density (t/m³)
Bulk bags = tonnes ÷ bag size
Tonnes = volume × density (t/m³)
Bulk bags = tonnes ÷ bag size
How deep should gravel be?
| Job | Typical depth |
|---|---|
| Decorative gravel border | 30 to 50 mm on membrane |
| Garden path | 40 to 50 mm on a compacted base |
| Gravel driveway top layer | 40 to 50 mm on 100 to 150 mm of MOT Type 1 |
| Sub-base under a patio | 100 to 150 mm of MOT Type 1 |
Worked example
A 6 m × 3 m driveway topped with 50 mm of gravel needs 0.9 m³, which is about 1.44 tonnes at 1.6 t/m³: 2 bulk bags of 850 kg. The 150 mm MOT Type 1 base under it is another 2.7 m³, about 5.7 tonnes.
Frequently asked questions
How much gravel do I need for a driveway?
For a 6 m by 3 m driveway with a 50 mm top layer, about 1.44 tonnes, or 2 bulk bags of 850 kg.
How many tonnes is a cubic metre of gravel?
About 1.6 tonnes for most gravel and shingle, and around 2.1 tonnes for compacted MOT Type 1.
How much does a bulk bag of gravel cover?
An 850 kg bag covers about 10.6 m² at 50 mm deep, or about 17.7 m² at 30 mm.
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Last updated October 2026.