How much soil to fill a raised bed? Enter its inside size and fill depth to see how much soil to buy, in cubic yards, cubic feet and bags.
How to use the soil calculator
- Pick a rectangle or a circle and enter the size of the area. Break L-shapes and curves into simpler pieces and add the results.
- Enter the depth you want once the material is spread and levelled. Depth is usually easiest in inches.
- Keep an allowance for settling and low spots unless the ground is already flat and firm.
- Check the weight per cubic yard against your supplier’s figure, then add a price to get a cost estimate.
Soil formulas
Volume (ft³) = length (ft) × width (ft) × fill depth (ft) Cubic yards = cubic feet ÷ 27 Bags = cubic feet ÷ bag size (cu ft), rounded up
Bagged soil is sold by the cubic foot and bulk soil by the cubic yard, so the calculator gives both and lets you compare the price either way.
Worked example: 8 × 4 ft at 12 in deep
- Volume: 8 ft × 4 ft × 1.00 ft = 32.0 ft³.
- Cubic yards: 32.0 ÷ 27 = 1.19 yd³.
- Bags of 2 cu ft: 32.0 ÷ 2 = 16 bags.
- Weight: 1.19 yd³ × 2,000 lb = about 2,380 lb.
How deep to go
Fill depth is the soil, not the height of the frame — most gardeners leave 1–2 in of freeboard at the top so water does not run over the edge. For more than one bed of the same size, multiply the result by the number of beds.
Soil per bed depth
| Fill depth | One cubic yard fills | Per 100 ft² of bed | Bags of 2 cu ft per 100 ft² |
|---|---|---|---|
| 6 in | 54 ft² | 1.85 yd³ | 25 bags |
| 8 in | 40 ft² | 2.47 yd³ | 33 bags |
| 10 in | 32 ft² | 3.09 yd³ | 42 bags |
| 12 in | 27 ft² | 3.70 yd³ | 50 bags |
A cubic yard is 27 cubic feet, so a 4 × 8 ft bed filled 12 in deep takes just over a cubic yard. Bagged soil is sold by the cubic foot, which is why the bag counts climb quickly on larger beds.
Questions
How much soil do I need for a 4 × 8 raised bed?
A 4 × 8 ft bed filled 12 in deep takes 32 cubic feet, which is 1.19 cubic yards, or 16 bags of 2 cu ft.
How many bags of soil make a cubic yard?
27 bags of 1 cu ft, 18 bags of 1.5 cu ft, 13.5 bags of 2 cu ft or 9 bags of 3 cu ft. A cubic yard is 27 cubic feet.
How deep should a raised bed be?
6–8 in suits lettuce, herbs and most greens. 10–12 in is better for tomatoes, peppers and root crops, which need the depth to root.
Is it cheaper to buy soil in bulk or in bags?
Bulk by the cubic yard is almost always cheaper once you need more than about 10–12 bags, which is roughly a single 4 × 8 bed. Below that, delivery charges usually make bags the better deal.
How many 1.5 cu ft bags fill a 4 × 8 bed 12 in deep?
4 × 8 × 1 = 32 cu ft, so 22 bags (21.3 rounded up), or about 1.2 cubic yards bulk.
Sources
- Landscape Materials Density Chart, North Bay Materials.
Used for: Typical weights per cubic yard for gravel, crushed rock, soil and mulch. - NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Exact inch and foot definitions; cubic foot and cubic yard conversions.