Raised Bed Soil Calculator
Estimate how much soil your raised garden beds need. Enter bed size, soil depth, and the number of beds, then optionally plan a soil, compost, and amendment mix.
Results
Enter your measurements to see an estimate.
Calculated: — EasyBuildTools, www.easybuildtools.com
How to use the Raised Bed Soil Calculator
Enter the interior length and width of one bed in feet, the soil depth in inches, and how many identical beds you are filling. Choose a bag size (or set a custom bag volume) to estimate bag counts. Optionally enable the soil-mix planner to break the total into topsoil, compost, and an aeration amendment by percentage.
Formula and methodology
- Volume per bed = length × width × (depth ÷ 12), in cubic feet.
- Total volume = volume per bed × number of beds.
- Cubic yards = total cubic feet ÷ 27.
- Bags = total cubic feet ÷ bag volume, rounded up.
- Mix components = total volume × each percentage ÷ 100. Percentages must total 100.
Worked example
Bed: 4 ft × 8 ft, 12 in deep, 2 beds. Volume per bed = 4 × 8 × (12 ÷ 12) = 32 cu ft. Total = 64 cu ft = 2.37 cu yd. With 2 cu ft bags: 64 ÷ 2 = 32 bags. Using a 40/40/20 mix: 25.6 cu ft topsoil, 25.6 cu ft compost, 12.8 cu ft amendment. Enter the values above to confirm.
Choosing a soil mix
There is no single correct raised bed mix. A common starting point is roughly equal parts quality topsoil, compost, and an aeration amendment such as perlite, vermiculite, or coarse sand — then adjusted for what you grow. Leafy greens and root crops prefer different drainage; heavy clay native soil changes how much aeration you want; wet climates benefit from more drainage, dry ones from more water-holding organic matter. The mix planner is a convenience, not a recipe, so adapt it to your crops, native soil, climate, drainage, and the products available locally.
For filling large beds from bulk topsoil, the Topsoil Calculator handles lawns and beds by area. For mulching the top of finished beds, see the Mulch Calculator, and read How Much Soil Does a Raised Garden Bed Need? for depth and mix guidance.