Quick answer
Soil depth depends on what is being grown, existing soil and the bed construction. Measure the inside bed area, choose a planting-appropriate depth, multiply area by depth in feet and convert the result to yards or bags.
Step by step
- Measure inside dimensions Do not use the outside frame if the walls have thickness.
- Check existing soil The bed may not need to be filled from zero.
- Set target depth Use crop or horticultural guidance.
- Convert quantity Divide cubic feet by 27 or by bag volume.
Formula or rule of thumb
soil volume(ft³) = length × width × depth(ft); yd³ = ft³ ÷ 27
Example
A 4 × 8 ft bed filled 12 in deep needs 32 ft³, about 1.19 yd³.
Common mistakes
Ignoring existing soil, using outside dimensions, and assuming a bag's volume from its weight.
Planning note: product yields, installation methods, site conditions and local requirements can change the final quantity. Use the exact manufacturer or supplier information before purchasing.
FAQ
Should soil depth be the same for every crop?
No. Rooting needs differ.
How many bags per yard?
27 ÷ cubic feet per bag.
Does soil settle?
Bulk material can settle; ask the supplier how delivered volume is represented.