GardenCalcs.uk
Gravel Calculator — How Much Gravel
Work out gravel quantities in tonnes or bulk bags for drives and paths.
Adds a margin for compaction, levelling and spillage so you do not run short. Adjust the percentage under Advanced Options.
How We Calculate This
Volume = Length × Width × Depth (depth converted from cm to metres). Weight = Volume × Density, where decorative gravel is about 1.5 t/m³, pea gravel 1.6, limestone 1.5 and slate chips 1.4. Bulk bags are ordered at 850kg each (a typical UK "tonne" bag), and the same weight is also shown as 25kg bags for smaller top-up jobs.
Frequently Asked Questions
Paths: 3-5cm. Drives: 5-7cm. Decorative: 3-4cm. Deeper is more stable but uses more material.
Approximately 1.5 tonnes per cubic metre for most gravels. Slate chips are slightly lighter.
A bulk (or "tonne") bag holds roughly 0.5m³ and weighs about 850kg of gravel, despite the nickname. This calculator orders bulk bags at 850kg each, so it allows for the fact that one bag is not a full tonne. At 50mm depth an 850kg bag covers roughly 10-12m².
Yes, always lay a weed membrane before gravel on paths and drives. It prevents weeds growing through and stops gravel mixing into the sub-soil.
10-20mm is the most popular for paths and drives. Smaller (6-10mm) works for decorative beds. Larger gravel (20-40mm) is harder to walk on and shifts more.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.