Measure inside dimensions. Use the unfilled percentage only for known false bottoms, large permanent fillers or other measured displacement—not anticipated settling.
01 / Formula
How this is calculated
Soil volume = length × width × depth × (1 − unfilled %) × (1 + allowance %)02 / Assumptions
What the estimate assumes
- ✓Dimensions describe usable interior space.
- ✓The unfilled percentage represents real displaced volume.
- ✓Mix composition and settling are selected separately.
03 / Worked example
See the math in context
An 8 × 4 ft bed filled 18 inches deep has 48 cubic feet of gross volume before displacement and allowance.
04 / Guidance
Separate volume from soil choice
Bed depth does not determine the correct soil blend. Match the growing medium to crops, drainage, existing soil, climate and trusted horticultural guidance.
Questions
Frequently asked
How do I measure an irregular area?+
Split the bed or lawn into rectangles, circles, and triangles, calculate each area, then add them. Measure narrow curves in shorter sections for a better approximation.
Should I include extra material?+
Use a visible allowance for grade variation, settlement, compaction, spillage, cuts, or future repair as appropriate. The right percentage depends on the material and site.