Garden soil calculator

Work out how much soil, compost or topsoil a bed needs before you order it — in cubic feet, cubic yards, cubic metres or litres.

Garden soil calculator

Everything is worked out in your browser — nothing is sent anywhere.

Length

Width

Length & width unit

Depth

Depth unit

Cubic feet: 32.00
Cubic yards: 1.19
Cubic metres: 0.91
Litres: 906

Roughly 43 standard 0.75 cu ft bags of soil or compost. Order about 5–10% extra to allow for settling.

What this calculator works out

It calculates the volume of growing medium needed to fill a rectangular bed, border, planter or trench to a chosen depth. Suppliers sell soil and compost by volume — bags in cubic feet or litres, bulk deliveries in cubic yards or cubic metres — so volume is the number you actually need before buying.

How to use it

Measure the inside length and width of the bed.
Decide how deep the new soil layer should be.
Enter the three figures and pick the matching units.
Read the volume, then add 5–10% for settling and compaction.

The formula

Convert every measurement to feet, then multiply: length × width × depth gives cubic feet. Divide cubic feet by 27 for cubic yards, because a cubic yard is 3 × 3 × 3 feet. Multiply cubic feet by 28.317 for litres.

Worked example

A bed 8 ft long and 4 ft wide, filled 12 inches (1 ft) deep: 8 × 4 × 1 = 32 cubic feet. That is 32 ÷ 27 = 1.19 cubic yards, or roughly 43 standard 0.75 cu ft bags.

How deep should the soil be?

Topping up an existing bed: 2–4 inches of compost is usually enough.
New vegetable beds: 8–12 inches gives most crops room to root.
Root crops such as carrots and parsnips: aim for 12 inches or more of loose, stone-free soil.
Shallow-rooted salads and herbs: 6–8 inches works well.

Buying tips

Bulk soil is cheaper per unit than bags once you pass roughly one cubic yard, so it is worth comparing both. Bear in mind that fresh compost settles: a bed filled to the brim in spring often drops an inch or two by midsummer, which is normal and easily topped up.