Raised Bed Soil Calculator
How much soil to fill your raised beds, and how much of each ingredient for the mix you choose, in bags or bulk yards, with an option to save soil with logs or branches at the bottom.
Soil (cu ft) = length (ft) × width (ft) × depth (in) ÷ 12, plus about 10% for settling. A 4 × 8 ft bed 12 in deep needs about 35 cu ft (1.3 cu yd), or 24 bags of 1.5 cu ft. Several beds? Bulk delivery is usually cheaper above about 1 cubic yard.
Soil for common raised bed sizes (+10% settling)
| Bed | Depth | Cubic feet | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|---|
| 4 × 4 ft | 6 in | 8.8 | 0.33 | 6 |
| 4 × 4 ft | 12 in | 17.6 | 0.65 | 12 |
| 3 × 6 ft | 12 in | 19.8 | 0.73 | 14 |
| 4 × 8 ft | 6 in | 17.6 | 0.65 | 12 |
| 4 × 8 ft | 12 in | 35.2 | 1.30 | 24 |
| 4 × 8 ft | 18 in | 52.8 | 1.96 | 36 |
| 2 × 8 ft | 12 in | 17.6 | 0.65 | 12 |
Raised bed soil mixes
| Mix | Recipe | Good for |
|---|---|---|
| Topsoil-based | 60% topsoil, 30% compost, 10% perlite or fine bark | Deep beds and budgets; holds moisture |
| Mel's Mix | ⅓ compost (blended), ⅓ peat or coir, ⅓ coarse vermiculite | Square-foot gardens 6 in deep |
| Bagged raised bed mix | Ready to use | Small beds and convenience |
Frequently asked questions
How much soil do I need for a 4 × 8 raised bed?
About 35 cubic feet for a bed 12 in deep, including 10% for settling: that is 1.3 cubic yards or 24 bags of 1.5 cu ft. At 6 in deep it takes about 18 cu ft.
How deep should a raised bed be?
6 in works for lettuce, herbs and shallow-rooted crops over loosened ground; 10–12 in suits most vegetables; 18–24 in helps carrots, potatoes and beds on hard or paved ground.
What is the best soil mix for raised beds?
A blend of about 60% screened topsoil, 30% compost and 10% perlite or fine pine bark drains well and holds nutrients. Square-foot gardeners use Mel's Mix: equal parts compost, peat or coir, and coarse vermiculite.
Can I put logs or branches in the bottom of a raised bed?
Yes, in deep beds. Logs, branches and leaves at the bottom (a hugelkultur-style base) save soil and hold moisture as they break down. Expect the surface to sink a little each year and top it up with compost.
Is it cheaper to buy soil in bags or bulk?
Bags win for one small bed. Above about 1 cubic yard (27 cu ft), bulk delivery from a landscape supplier usually costs much less per cubic foot, even with a delivery fee.
Run a garden club, nursery or landscaping site? Embed this calculator free with one line of code.
Related free tools
Potting Soil Calculator
Quarts and bags of potting mix for pots, planters and grow bags.
Open tool →Topsoil Calculator
Cubic yards, tons, bags and truckloads of topsoil for lawns, beds and gardens.
Open tool →Fertilizer Calculator
Pounds or ounces of any N-P-K fertilizer per 1,000 sq ft and for your whole lawn.
Open tool →Sod Calculator
Square feet, pallets, slabs or rolls, topsoil and cost for any lawn shape.
Open tool →Sources and assumptions
Volume = length × width × depth; 10% is added because fresh soil settles. Mix ratios are common gardening recipes; Mel's Mix is from the Square Foot Gardening method. Bag sizes reflect typical retail sizes (topsoil 0.75 cu ft, compost 1 cu ft, raised bed mix 1.5 cu ft).