YardRaised bed soil formula
Cubic yards = Cubic feet ÷ 27
Bags = Cubic feet ÷ bag size
Soil for common raised bed sizes
| Bed size | Depth | Cubic feet | Cubic yards | 1.5 cu ft bags | 2 cu ft bags |
|---|---|---|---|---|---|
| 4 × 4 ft | 12 in | 16 | 0.59 | 11 | 8 |
| 4 × 8 ft | 12 in | 32 | 1.19 | 22 | 16 |
| 4 × 8 ft | 18 in | 48 | 1.78 | 32 | 24 |
| 3 × 6 ft | 12 in | 18 | 0.67 | 12 | 9 |
| 2 × 8 ft | 12 in | 16 | 0.59 | 11 | 8 |
| 4 × 12 ft | 12 in | 48 | 1.78 | 32 | 24 |
For several beds or more than about a cubic yard, bulk soil delivery is often cheaper than bags. Try the topsoil calculator for other sizes.
What soil to use
Most gardeners fill raised beds with a blend of good topsoil and compost, sometimes with a lighter material added for drainage. Ready-made "raised bed mix" is the simplest option. Avoid plain fill dirt – it has little organic matter.
Filling a deep bed for less
- Logs and branches at the bottom (the hügelkultur idea) take up space and break down slowly.
- Leaves, straw and grass clippings can fill the lower layers; they will shrink, so top up next year.
- Cardboard on the ground smothers grass and weeds before you fill.
- Keep at least 8–12 inches of good soil on top where the roots grow.
Topping up each year
Soil in raised beds settles and compost breaks down, so expect to add a few inches each season. Measure the gap from the soil to the top of the bed and use that depth in the calculator.
Frequently Asked Questions
How much soil do I need for a 4x8 raised bed?
At 12 inches deep, 32 cubic feet – about 1.19 cubic yards or 16 bags of 2 cu ft soil.
How many bags of soil for a 4x4 raised bed?
At 12 inches deep, 16 cubic feet: 8 bags of 2 cu ft or 11 bags of 1.5 cu ft.
Is bulk soil cheaper than bags?
For more than about a cubic yard it usually is, but compare local prices including delivery.