A little less waste. A lot more possibility.Practical tools for your next garden habit

THE RAISED BED SOIL CALCULATOR

Raised bed
soil calculator.

Work out the volume for a rectangular bed or a layer of compost. Choose US or metric units, then match the volume printed on your bags.

YOUR BED

Enter the depth you need to fill with a suitable soil mix.

Use the bag’s volume, not its weight. The optional allowance adds 0–30% to your estimate; 0% is the default.

YOUR VOLUME ESTIMATE

Room for something good.

Enter your measurements and select Calculate volume.

This is a volume calculation, not a compost application recommendation. Choose amendment depth from your soil test and local guidance.

How many bags of soil for a 4×8 raised bed?

At 12 inches of fill depth, one 4×8-foot bed holds 32 cubic feet (about 1.19 cubic yards or 906 liters). That equals 16 bags at 2 cubic feet each, with no extra allowance. Use the inside measurements and the depth still empty in your bed.

The simple volume formula

US: length (ft) × width (ft) × depth (in) ÷ 12 × number of beds = cubic feet. Divide by 27 for cubic yards. Metric: length (m) × width (m) × depth (cm) ÷ 100 × number of beds = cubic meters. Multiply by 1,000 for liters. Divide by bag volume and round up.

For a compost top-up, measure only the layer being added. A half-inch layer on the same bed needs about 1.33 cubic feet (38 liters), rather than 32 cubic feet of compost. Oregon State Extension explains the area × depth method and why raised beds need a soil mix rather than compost alone.

How much compost does a raised bed need?