How to use the topsoil calculator
- Choose metric or imperial units and the shape of the area.
- Enter the length and width (or diameter), and the depth of new soil you want.
- Leave the settling allowance at 10% (15–20% for raised beds), and say how wet the soil is.
- Buying bags? Enter the bag size from the label to get a bag count.
The formula
volume = area × depth × (1 + settling %)
weight = volume × density (low to high for the soil's moisture)
bags = volume ÷ bag size (rounded up)
Worked examples
Metric: a 6 m × 4 m lawn area, 10 cm deep: 6 × 4 × 0.1 = 2.4 m³, plus 10% = 2.64 m³, which weighs about 3.4–4.2 tonnes when moist. In 25-litre bags that would be 106 bags — a good sign a bulk load is the better buy.
Imperial: a 20 ft × 15 ft area, 4 in deep: 100 ft³ = 3.70 yd³, plus 10% = 4.07 yd³, about 4.5–5.5 US tons when moist.
Choosing the depth
The right depth depends on the job — topping up a tired lawn needs far less than building a new bed or levelling a slope. Check the advice for your plants or turf, then enter that depth here. If you're filling a raised bed, enter the inside length, width and the depth you want to fill.
Tips before you order
- Ask how it's sold. Topsoil may be priced per tonne, per cubic metre or cubic yard, per bulk bag, or per small bag. The calculator gives you each measure.
- Check what's in a bulk bag. "Bulk bag" sizes differ between suppliers — ask for the volume or weight.
- Wet weather adds weight. Soil delivered after rain is heavier, so weight-based orders contain less soil. Choose “Wet” in the calculator to see the difference.
Common mistakes to avoid
- Ignoring settling. Loose soil sinks after watering and rolling — keep an allowance.
- Confusing bag sizes. A small retail bag (in litres) and a builder's bulk bag are very different volumes.
- Ordering by weight in wet weather. Wet soil is heavier, so a tonne contains less soil.
Measuring an awkward shape? See how to measure an irregular area.
Frequently asked questions
How much does a cubic metre of topsoil weigh?
It depends mostly on how wet it is. Published figures: dry about 1.19–1.54 t/m³, moist (a typical delivery) about 1.3–1.6 t/m³, and wet about 1.78–2.02 t/m³. In US units that is roughly 1–1.3, 1.1–1.35 and 1.5–1.7 US tons per cubic yard. Choose the condition in the calculator and you'll see the weight range.
Does wet topsoil change how much I need?
Not the volume — you still need the same amount of space filled. But wet soil is heavier, so if you buy by the tonne or ton you get less soil for your money, and a trailer or truck reaches its weight limit sooner. If you buy by the cubic metre or cubic yard, moisture doesn’t change your order.
How much soil for a 4 × 8 ft raised bed?
A 4 × 8 ft bed filled 12 in deep holds 32 cubic feet (1.19 cubic yards). Soil in raised beds settles after watering, so guides suggest adding 10–20%. With 15% that's about 1.36 cubic yards, or 37 cubic feet of bagged soil.
How much area does a tonne of topsoil cover?
For moist topsoil at the heavy end (1.6 t/m³), one tonne is about 0.63 m³, which covers roughly 6.3 m² at 10 cm deep. Drier soil covers a little more. Use the calculator for your own depth.
Should I buy bags or a bulk load?
Bags are convenient for small beds and planters and easy to carry through a house. For larger areas, a bulk bag or loose load is usually cheaper per cubic metre. Compare the price per cubic metre (or cubic yard) rather than per bag — the calculator shows the volume so you can do that.
Why add extra topsoil?
Loose topsoil settles after it is spread, watered and walked on, and ground is rarely perfectly level. We add 10% by default; guides suggest 10–20% for raised beds, so increase it there, or if you are filling hollows.
Sources
Last updated 11 November 2026. Found a mistake? Tell us.