Topsoil calculator
Estimate topsoil volume for a chosen surface layer over a bed, border or levelling area from its area and depth. Raised-bed fill and compost mulching are different tasks.
Result
Topsoil required
Bags needed (25L)
How to use this tool
- Measure the length and width of the surface area, then enter the topsoil layer depth selected for the project.
- Enter the three dimensions — switch units if you measured in feet or inches.
- Read the estimated volume and bag equivalent based on the assumed package size; check the product label or bulk supplier units.
Assumptions
- Bag count assumes 25L per bag and rounds up; it is exact only if the package volume matches that assumption. Check the package, and use supplier quantity units for bulk products.
- The formula does not model soil density, moisture, settlement or delivery quantity. The entered waste allowance is not a material-specific yield factor.
Technical details: what the fields mean
- Length
length - The longest side of the area to fill.
- Width
width - The other side of the area to fill.
- Depth
depth - Chosen layer depth. The entered dimensions determine volume; select depth for the project and soil use rather than relying on a universal figure.
- Waste allowance
wastePercent - Optional editable allowance for uneven ground or settlement; the default is illustrative.
Methodology
Geometric volume = length × width × depth. The editable waste allowance is applied to that volume; bag count assumes 25L per bag. Use the actual package volume if it differs.
Worked example
3m × 2m area, chosen 100mm topsoil layer, 10% allowance
Inputs: Length: 3 m, Width: 2 m, Depth: 0.1 m, Waste allowance: 10%
Result: 0.66 m³ required, 27 bags
Practical guidance
- Compare bagged and bulk quotes for the quantity you need, including package volume, delivery and supplier terms.
- Mix in compost for planting beds — pure topsoil alone is often low in organic matter.
Common mistakes
- Treating the entered depth or waste allowance as a universal soil-layer or yield recommendation.
- Confusing topsoil for a surface layer with the soil mix needed to fill a raised bed.
FAQs
How much topsoil do I need for a 3m x 2m area?
For a chosen 100mm topsoil layer and 10% allowance, the estimate is 0.66m³. Bag count uses the calculator's assumed 25L per bag; check actual package volume. This is a surface-layer estimate, not raised-bed fill.
Should I buy bagged or bulk topsoil?
Compare local supplier prices for the amount, product and delivery terms you need; package sizes, bulk units and costs vary.
Last reviewed: 2026-10-11
A simple rectangular-area estimate — doesn't account for sloped ground or an irregular bed shape.
This tool provides an indicative estimate, based on the assumptions stated above.
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