BuildCalcs Topsoil Calculator
Estimate how much topsoil you need from the area and depth, with tonnes, bulk bags and litre bag equivalents.
Topsoil volume calculation
Length × width × depth gives the volume required. The calculator converts the result into litres and uses the chosen density to estimate tonnes and bulk bags.
Choosing a soil depth
The appropriate depth depends on whether you are topping up an existing lawn, filling a raised bed or establishing a new planting area. Use the specification for your particular project rather than assuming one depth suits every use.
Frequently asked questions
How many litres are in one cubic metre?
One cubic metre equals 1,000 litres.
Why is the weight approximate?
Wet soil is heavier than dry soil and the blend of mineral material and organic matter also changes bulk density.
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Estimating topsoil volume
Topsoil quantity is driven by area and finished depth. The calculator converts depth from millimetres to metres, multiplies by area and then estimates tonnes using the planning density. A 10 m by 5 m area at 100 mm deep is 5 m³ before allowance, showing why apparently small changes in depth have a large effect on an order.
Bulk density is variable
Soil weight changes with composition, screening and moisture content. The density input therefore provides a planning conversion rather than a guaranteed delivery weight. When buying loose soil or bulk bags, use the supplier's stated bag weight or volume where available and compare it with the calculator's cubic-metre requirement.
Allow for settlement and site levels
Freshly placed topsoil can settle, especially where it is spread over recently disturbed ground. Finished depth should also account for turf, mulch or other surface layers if they form part of the project. Do not use topsoil to replace a structural sub-base or to solve drainage problems. For irregular gardens, calculate separate rectangles and add them before applying an allowance.