How the soil calculator works

For each area: new volume = footprint × (final fill depth − existing fill depth) × number of identical areas. A rectangle uses length × width; a circle uses π × diameter² ÷ 4. Add all new volumes, then add your chosen ordering allowance. Measurements describe average level layers; sloping or uneven ground needs an appropriate measured average.

Whole bags are rounded up after combining areas. Bulk orders respect your minimum and order increment. When no new soil is needed, the calculator does not apply a minimum order or delivery charge. Displayed volumes are rounded for reading; purchasing uses the unrounded result.

Which units should I use?

There are 27 cubic feet in one cubic yard. One cubic foot is 28.316846592 litres. One US dry quart is about 1.101221 litres, unlike a US liquid quart. Use the exact unit on the package. Switching measurement units converts your existing dimensions; bag and bulk units remain independently selectable. Changing a purchasing unit converts its entered quantity and unit price without changing the quote.

Can I calculate the weight of topsoil?

This calculator estimates volume, not weight. Soil density varies with composition and moisture. For a supplier selling by weight, request their volume-to-weight conversion for the actual product. Do not use a universal tons-per-yard assumption.

Does the result tell me which soil or depth to choose?

No. The example depths demonstrate arithmetic, not planting recommendations. Choose a suitable growing medium and target depth for your plants and site. Existing fill is subtracted geometrically; the calculator does not assess its quality, drainage or suitability.

Sources and related projects

NIST volume conversions; NIST dry-volume table; Gardener’s Supply soil-planning examples.

Planning individual plants in a rectangular bed? Use the plant spacing calculator for centre positions, row layouts and whole-pack ordering.

For a new lawn above the prepared soil, use the sod calculator to plan rolls, pallets and your installation budget. If you are sowing seed, use the grass seed calculator to plan whole bags from your product label, including overseeding and seed already available.

For the separate protective layer above your soil, use the mulch calculator to compare bags and bulk delivery after subtracting existing mulch.

For a separate aggregate path or base, use the gravel calculator. For the blocks around a supported soil area, use the retaining wall calculator; it does not replace structural design.