Raised bed soil volume formula
For a rectangular raised bed, multiply the inside length by the inside width by the intended soil depth. Keep all measurements in the same unit before multiplying.
Volume = length × width × depth
For example, an 8 ft × 4 ft bed filled 12 in deep uses 32 cubic feet, before adding a reserve for settling.
Common raised bed volumes
| Bed size | Depth | Approx. volume |
|---|---|---|
| 4 × 4 ft | 12 in | 16 ft³ / 453 L |
| 4 × 8 ft | 12 in | 32 ft³ / 906 L |
| 3 × 6 ft | 10 in | 15 ft³ / 425 L |
| 1 × 2 m | 30 cm | 0.6 m³ / 600 L |
Why add a reserve?
Bagged soil and compost settle after filling and watering. Uneven ground, rounded bed corners and measurement differences also affect the final level. A reserve of around 5–15% is a practical shopping buffer, but you can change it in the calculator.
Bagged soil or bulk delivery?
Small beds are convenient to fill with bags. For several large beds, compare the total cubic-yard or cubic-metre result with local bulk delivery. Remember that delivery products may be sold by loose volume and can compact after transport.
What should go into a raised bed?
There is no universal mix for every climate and crop. A typical starting structure combines mineral soil, mature compost and a material that maintains drainage and air space. Avoid treating any fixed ratio as a substitute for local soil knowledge.