Gravel Calculator

Gravel is sold by volume (cubic metres or cubic yards) and sometimes by weight (tonnes or kilograms). To find out how much you need, you first calculate the volume of the space you want to fill: multiply the area's length by its width, then by the intended depth of the gravel layer. For circular areas such as round garden beds or ponds surrounds, use the formula for a circle's area (π × radius²) multiplied by depth. Converting depth from centimetres to metres is essential so that all units remain consistent.

The volume formula for a rectangular or path-shaped area is V = L × W × D, where L is length in metres, W is width in metres, and D is depth in metres. For a circular area, the effective area becomes π × (diameter ÷ 2)². Once you have the volume in cubic metres, multiply by the gravel's bulk density (in kg/m³) to find the weight. Bulk density varies — dry, loose gravel typically measures around 1,500 kg/m³, a typical mixed and slightly settled gravel runs around 1,600 kg/m³, and wet or heavily compacted gravel can reach 2,000 kg/m³. Choosing the right density matters because suppliers often sell gravel by the tonne.

Practical applications include planning driveway resurfacing, filling raised garden beds, installing French drains or soakaways, laying gravel paths through gardens, and creating decorative landscaping features. Professional landscapers use this type of calculation before every project to generate accurate material quotes, while DIY homeowners rely on it to avoid multiple supplier trips. Always add a 10–15% buffer to your calculated quantity to account for wastage, compaction, and uneven ground surfaces.

This calculator assumes a flat, level surface with uniform depth throughout. For sloped driveways or uneven terrain, the actual volume needed may be significantly higher and should be assessed on-site. Bulk density values are estimates — gravel type (pea gravel, crushed stone, slate, quartzite) and moisture content both affect real-world density. Always verify the density with your supplier before ordering large quantities. The calculator does not account for sub-base preparation layers, which are often required beneath decorative gravel in driveways to prevent sinking. Additionally, compaction means that the laid gravel will settle to a depth slightly less than intended over time — factor in 10–15% extra depth if long-term appearance is critical. For very large commercial projects, a civil engineering survey and specification are recommended rather than a simple volume estimate.