Overview
What is the Topsoil Calculator?
A topsoil calculator is a coverage estimator for loose garden soil, screened topsoil, and raised-bed blends. You describe the area (or trench) you are filling, set a depth that matches your project type, choose a soil type — or a custom density — and optionally add waste and compaction. The tool returns volume, weight, and bag counts. It does not replace a soil test or a landscape architect's grading plan for large regrades.
Topsoil orders go wrong in familiar ways: a raised-bed depth measured in centimetres gets typed in as inches, a new-sod job is ordered as if the whole yard needed the same depth as a thin top dressing, or a delivery quoted in cubic yards gets compared against a garden-centre price per litre bag with no common unit in between. This free topsoil calculator turns rectangles, circles, triangles, trenches, known areas, and known volumes into cubic yards and cubic metres, then adds waste and a compaction allowance for settlement, so you can order the right amount for a lawn, new sod, a raised bed, or a garden — in yards, litres, tons, tonnes, or bags.
Workflow
How does it work?
Volume is area × depth for most modes. Rectangle and trench use length × width. Circles use πr² from diameter. Triangles use ½ × base × height. Known-area mode skips plan dimensions. Known-volume mode converts ft³, yd³, m³, litres, or US gallons straight into weight. The raw volume is multiplied by (1 + waste%/100) for spill and by (1 + compaction%/100) to allow for settling once the soil is watered and beds are walked on. Weight multiplies the final volume by the bulk density for the soil you selected. Bag counts divide the final volume in litres by common 20 L, 40 L, 50 L, and 70 L packs, plus 800 L bulk bags.
Choose Imperial or Metric, then select a topsoil type — or enter a custom density from your supplier ticket.
Pick Rectangle/garden bed, Circle, Triangle, Trench, Known area, or Known volume.
Enter the dimensions that enclose the soil layer, then set depth using the project-type chips (top dressing, new sod, lawn, flower bed, garden, vegetable, raised bed) or a numeric depth chip.
Set waste for spill and uneven subgrade, and compaction for settlement after watering and walking on new soil.
Choose a bag size — 20 L, 40 L, 50 L, 70 L, a bulk bag, or a custom litre size — if you are buying bagged soil.
Optionally add a unit price per bag, bulk bag, yard, metre, or ton for a materials-only cost estimate.
Read yards, metres, litres, gallons, tons, tonnes, and bag counts, then copy or share the result.
Math
Formula
Volume = Area × Depth × (1 + waste%) × (1 + compaction%)
Area depends on mode: length × width, πr², ½ × base × height, or a direct area entry. Depth is the thickness of the soil layer after grading. Waste covers spill and subgrade unevenness. Compaction adds extra volume up front so the finished, settled depth still matches your target once the soil is watered in and traffic compresses it. Weight = final volume × bulk density. Preset densities are planning values for moist topsoil and garden soil blends; wetter or compost-heavy mixes weigh differently — confirm with your supplier.
Inputs
Step-by-step variables
L / W
Length and width
Plan dimensions of a rectangular lawn area, garden bed, or trench footprint.
Ø
Diameter
Across a circular bed or tree ring. Radius is diameter ÷ 2.
b / h
Triangle base and height
Base and perpendicular height of a triangular plan — not soil depth.
D
Depth
Thickness of the topsoil layer. Top dressing is shallow; raised beds are deep.
ρ
Bulk density
Mass per cubic metre for the selected topsoil, or a custom kg/m³ from your yard.
Waste %
Waste allowance
Extra volume for spill, uneven subgrade, and material lost during placement.
Compaction %
Compaction allowance
Extra volume placed up front so the finished depth still meets your target after settling.
Practice
Step-by-step examples
New sod prep (imperial)
A 30 ft × 15 ft lawn area needs 3 in of topsoil before laying new sod, with 10% waste and 10% compaction.
Depth 3 in = 0.25 ft. Area = 450 ft². Raw volume = 112.5 ft³ ≈ 4.17 yd³. With 10% waste and 10% compaction (×1.21) ≈ 5.04 yd³ (about 3.85 m³). At ~1,250 kg/m³ (lawn topsoil) that is roughly 4.8 tonnes — likely a bulk delivery rather than bags.
On site
Real-life examples
Raised garden bed in metres
A raised bed 2.4 m × 1.2 m needs 300 mm of raised bed soil, with 5% waste and 15% compaction for a fresh, loose fill.
Area = 2.88 m². Raw volume ≈ 0.864 m³; with 5% waste and 15% compaction (×1.2075) ≈ 1.04 m³ (about 1,043 L, or roughly 26 bags of 40 L soil). Weight near 1.1 tonnes at 1,050 kg/m³ — most gardeners buy this in bagged raised-bed soil rather than by the yard.
Where it helps
Use cases
- Levelling and top-dressing an existing lawn
- Building up soil depth before laying new sod
- Filling raised garden beds and planter boxes
- Vegetable garden beds and flower borders
- Comparing bulk yard/tonne quotes against bagged garden-centre soil
Avoid these
Common mistakes
- Entering raised-bed depth in centimetres when the box is measured in inches
- Ordering top-dressing depth for an entire new-sod prep, which needs a much thicker layer
- Skipping a compaction allowance, then finding the bed sinks a few centimetres after the first watering
- Assuming every 40 L bag weighs the same regardless of moisture and blend
- Mixing lawn topsoil density with raised-bed soil density on the same order sheet
- Ignoring waste on long wheelbarrow runs from a bulk delivery pile to the bed
Buying & planning
Tips
- Use the project-type depth chips as a starting point, then adjust for your specific sod or seed supplier's recommendation.
- For irregular lawns, split the area into rectangles and triangles, then add the areas before entering a known area.
- Ask whether your supplier quotes screened or unscreened topsoil — screened soil is lighter and easier to spread evenly.
- Keep both cubic yards and litres on your order note when comparing a bulk delivery price against bagged soil.
- Add a higher compaction allowance for compost-heavy blends, which settle more than mineral topsoil after watering.
- For raised beds, measure inside dimensions of the frame, not the outside, to avoid over-ordering.
Need the bigger picture? Read our calculator disclaimer and accuracy policy.