Gravel Calculator
Enter your area, layer depth, and stone density to see the volume and weight of gravel you need.
Volume and weight
Get both cubic metres and tonnes, so you can order by whichever unit your supplier uses.
Density varies
Gravel density is approximate — around 1.5 t/m³, but anywhere from 1.4 to 1.7 t/m³ depending on the stone.
How much gravel do I need?
From area and depth to tonnes
A gravel calculator turns a coverage area and a layer depth into the amount of stone to buy. It works out the loose volume the layer occupies, then converts that to a weight using the gravel's bulk density — the two figures suppliers price against.
First find the volume — the area multiplied by the depth (converted from centimetres to metres). Then multiply that volume by the density to get the weight.
Volume = area × depth | Weight = volume × densityThe depth is entered in centimetres because that is how layers are usually specified, so the calculator divides it by 100 to get metres before multiplying. The density converts that volume into a weight you can order by the tonne.
Suppose you are covering a 10 m² path with a 5 cm decorative layer of standard gravel.
Convert the depth
5 cm ÷ 100 = 0.05 m.Find the volume
10 m² × 0.05 m = 0.5 m³.Convert to weight
0.5 m³ × 1.5 t/m³ = 0.75 t of gravel.
The depth you choose drives the answer. A typical decorative path or border sits around 5 cm, while a surface meant for walking or a driveway is firmer at 7–10 cm or more — doubling the depth doubles the gravel. Density matters too: most gravels fall between 1.4 and 1.7 t/m³ depending on the stone, so the weight shifts by roughly a fifth across that range for the same volume. Order by volume or by weight to suit your supplier, and treat both figures as the minimum the area needs.
The formula is exact, but a few real-world factors keep it an estimate.
Density and compaction are approximate
The default 1.5 t/m³ is a representative figure for loose gravel; your actual stone may be lighter or heavier, so use the supplier's quoted density when you can. Gravel also settles and compacts after laying, which slightly reduces the depth over time. For both reasons, ordering around 5–10% extra is sensible so you are not left short.