Which soil do you need?
Pick the soil for the job first, then work out the amount. Each type has its own calculator if you want more detail.
Topsoil
Screened soil from the top layer of the ground.
Best for lawns and levelling
Fill dirt
Subsoil with little organic matter. Compacts firmly.
Best for holes and raising ground
Potting mix
Light and free draining. Not real soil at all.
Best for pots and planters
How deep should soil be?
How does the calculation work?
Cubic yards = area (ft²) × depth (ft) ÷ 27
A bed 12 ft by 4 ft filled 8 in deep: 48 ft² × 0.67 ft = 32 ft³, or 1.2 yd³. That is 32 bags of 1 cu ft.
In metric: a bed 3.6 m by 1.2 m at 20 cm is 0.86 m³, or 864 litres.
Bags or bulk?
A cubic yard is 27 cubic feet, so it takes 27 one cubic foot bags to match one yard of bulk soil. Past about one cubic yard, bulk delivery is almost always cheaper and saves a lot of plastic.