Garden Soil Calculator — Beds, Yards and Bags
Size soil for one or more identical rectangular garden or raised beds, with a settlement factor and selectable retail bag volume.
What does the soil calculator calculate?
Multiply one bed’s inside length, width, and fill depth, then multiply by the number of beds. This calculator adds a settling allowance and converts the result to cubic yards and whole bags. It sizes volume only; use a planting-appropriate soil blend rather than filling deep beds indiscriminately.
Multiple garden-bed soil formula
Inside dimensions avoid counting wall thickness. Multiplying by bed count sizes identical beds, and the settlement factor helps maintain target fill height after watering and initial consolidation.
How to measure for an accurate estimate
- Measure clear inside dimensions; lumber, block, and metal wall thickness does not hold soil.
- Measure fill depth from the prepared bed bottom to the desired settled soil line.
- Group only beds with identical dimensions; calculate other sizes in separate runs.
- Subtract substantial false bottoms or permanent internal reservoirs from the entered depth.
Two raised vegetable beds
Two beds each measure 8 ft by 4 ft inside and need 12 in soil, with 10% settlement and 1.5-ft³ bags.
Net volume is 64 ft³; order 70.4 ft³, equal to 2.61 yd³ or 47 bags.Before you purchase material
- Choose a blend suited to crops, drainage, climate, and bed depth rather than price alone.
- Check bulk compost and soil test information when growing food or sensitive plants.
- Mix components consistently before filling instead of creating abrupt, poorly draining layers.
- Consider saturated soil weight and structural capacity for elevated beds, roofs, or balconies.
Common questions
How much soil does an 8-by-4 raised bed need?
At 12 inches deep, an 8-by-4-foot bed holds 32 cubic feet before settlement. At 18 inches it holds 48 cubic feet. Measure inside the walls and subtract any false bottom; then add a modest allowance for initial settling.
Can I fill a raised bed entirely with topsoil?
That may create poor structure or drainage depending on the topsoil. Raised-bed media often combines screened mineral soil with stable organic materials, but an appropriate recipe depends on bed depth, crops, climate, and local products. Seek local horticultural guidance before blending.
How do I convert soil bags to cubic yards?
Multiply the number of bags by cubic feet per bag, then divide by 27. For example, eighteen 1.5-cubic-foot bags equal 27 cubic feet, or one cubic yard. Use labeled volume, not bag weight, because moisture changes weight.
Should I account for soil settling in a raised bed?
Yes, fresh mixes commonly consolidate after placement and watering. The default 10% allowance is a planning value, not a guarantee. Avoid overfilling against materials that must remain dry, and top up later if the selected blend settles more than expected.
Sources and reference standards
- USDA Natural Resources Conservation Service — Soil Health Fact SheetsCurrent federal guidance on soil function, structure, health, and management.
- U.S. EPA WaterSense — Landscaping TipsFederal recommendations for water-efficient landscape planning and soil preparation.