How much topsoil do I need?

Topsoil is sold by the cubic yard when it is delivered loose and by the bag when it is not, and the settling allowance is what separates a calculation that works from one that leaves you a wheelbarrow short. Enter the area and the depth you want to build up, and this returns cubic yards, an approximate weight, and the equivalent in 40 lb bags.

Area length (ft)

Area width (ft)

Depth (in)

6 in for a new bed, 1-2 in for top-dressing a lawn.

Settling allowance (%)

Loose topsoil settles 10-20% once watered.

Topsoil needed

4.26yd³

Approximate weight 5.17 tons40 lb bags 154 bagsVolume 115.0 ft³

Density varies with moisture and clay content, so the tonnage is an estimate. Order by volume where possible and confirm the weight limit of any vehicle before collecting.

Six inches is a sensible depth for a new raised bed or a lawn that has been stripped. One to two inches is top-dressing, which improves an existing lawn without smothering it — more than an inch at a time and the grass struggles to come through. Loose topsoil settles by 10 to 20% once it is watered and walked on, which is why the default allowance here is 15% rather than a token 5%.

Weight matters as much as volume. Topsoil at about 90 lb per cubic foot is roughly 1.2 tons per cubic yard, so a 4-yard delivery is nearly five tons — more than most half-ton pickups are rated for, and a clear argument for delivery rather than collection.

How the calculation works

Volume (ft³) = length × width × depth ÷ 12, multiplied by (1 + settling ÷ 100). Cubic yards = cubic feet ÷ 27. Tons = cubic feet × 90 ÷ 2000. Bags = cubic feet ÷ 0.75, for a 40 lb bag that yields about three quarters of a cubic foot.

• Topsoil density of 90 lb/ft³ (loose, typical screened loam). Wet or clay-heavy soil is appreciably heavier.
• Depth is the finished depth you want, and the settling allowance is added on top of it — do not deduct it.
• A 40 lb bag yields about 0.75 ft³, which is the usual figure for screened topsoil in bags.
• The area is level and rectangular; slopes should be measured as an average depth and will still be approximate.

Sources: Loose topsoil density: ~90 lb/ft³ (about 1.2 tons per cubic yard); 40 lb bag yield: ~0.75 ft³

Worked examples

Questions

How many bags of topsoil make a cubic yard?

36 bags of 40 lb, at about 0.75 ft³ each. That is why bags stop making sense above a couple of yards.

How deep should topsoil be for a new lawn?

Four to six inches of good loam over a prepared subsoil. Less than four inches and the grass roots hit poor soil within weeks of the first dry spell.

How much does a yard of topsoil weigh?

About 1.2 tons at 90 lb/ft³, though wet or clay-rich soil can reach 1.5 tons. Check the supplier's figure if you are collecting rather than having it delivered.

Do I need to add compost?

Usually yes. Blending 20-30% compost into the top few inches gives better structure than topsoil alone, and many suppliers sell a pre-mixed screened blend.

Why add 15% for settling?

Loose soil is full of air. Once watered and walked on it compresses noticeably, and a bed filled exactly to the brim with loose soil ends up an inch or two low.

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Written and maintained by Sam Winters. Last updated 2026-11-04. Every figure is computed in your browser; nothing you enter is sent anywhere. Found an error? Tell me — accuracy reports get fixed first.