Topsoil Calculator

How to use this calculator

1. Measure the area; for raised beds use the inside dimensions.
2. Choose the depth: 4–6 in (10–15 cm) for new lawns, 8–12 in (20–30 cm) for raised beds.
3. Keep 10–20% extra — loose soil settles once watered and walked on.
4. Use the cubic yards / m³ figure for bulk delivery, or the bag count for small beds.

Method & assumptions

Volume = Length × Width × Depth × (1 + settling %)
Weight ≈ Volume × 1.3 t/m³ (typical, moist loose topsoil)
Bags = Volume ÷ bag size, rounded up

Settling %

extra to allow for compaction after placing

Density

varies 1.1–1.5 t/m³ with moisture and organic content

Assumptions & limits

• Weight is approximate; wet soil weighs more.
• Bag volumes are as labelled; some bags are sold by weight.

Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.

Worked examples

In depth: topsoil planning notes

How deep should topsoil be?

For a new lawn from seed or turf, 4–6 in (10–15 cm) of good topsoil over the subsoil gives roots room to establish. For overseeding or levelling an existing lawn, a top-dressing of ¼–½ in (5–10 mm) is enough — any more smothers the grass. Raised vegetable beds are usually filled 8–12 in (20–30 cm) deep, often with a blend of topsoil and compost. Flower borders benefit from 6–8 in (15–20 cm) of improved soil.

If you are filling raised beds, consider putting coarse organic material in the bottom of very deep beds to reduce the volume of bought soil, and top with a quality blend. Topsoil settles as it is watered, often by 10–20%, so the calculator includes a settling allowance by default.

Bags, bulk and quality

Bagged topsoil and compost are sold by volume — 0.75–1.5 cu ft bags in the US and 25–70 L bags elsewhere. For more than about a cubic yard or cubic metre, bulk delivery is far cheaper, either loose from a tipper or in a 0.7–1 m³ bulk bag. Loose topsoil weighs about 1.1–1.5 tonnes per cubic metre depending on moisture and composition; our 1.3 t/m³ default is typical for moist screened soil.

Quality varies widely. Screened topsoil has had stones and roots removed, and blended products may include compost or sand. In the UK, BS 3882 is a recognised specification for topsoil; elsewhere, ask the supplier for a description or a sample. For vegetable beds, check that the soil is not contaminated, especially if it comes from an unknown site.

Spread topsoil when it is not waterlogged, rake it level, and firm it lightly before seeding. Avoid burying the base of existing trees under more than an inch or two of new soil.

Testing the soil you have

Before buying topsoil, it can be worth testing what you already have. A simple pH and texture check tells you whether the existing soil only needs compost and lime or sulphur rather than replacing. Adding a few inches of new topsoil over compacted clay without loosening it first can create a drainage problem at the boundary between the layers, so break up the subsoil before spreading.

Tips & common mistakes

• Ask for screened topsoil to avoid stones and roots.
• Don't pile soil against house walls or above the damp-proof course.
• Raised beds often use a 60/40 topsoil/compost mix — calculate the total and split it.

Sources

1. RHS (UK) – soil types and improvement — checked 2026-10; verify before launch
2. University of Minnesota Extension – soil for raised beds — checked 2026-10; verify before launch
3. USDA NRCS – soil bulk density — checked 2026-10; verify before launch

Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.

Cite or embed this calculator

DIYCalcLab. “Topsoil Calculator.” Oct 18, 2026. https://diycalclab.com/landscaping/topsoil-calculator/

An embeddable version for blogs and contractor sites is planned.