Reference formulas and worked examples below keep their stated units. Monetary examples use USD; dimensional examples use US customary units unless labeled otherwise. Metric calculator inputs are converted to these reference units before calculation. Choosing another currency does not convert example amounts or exchange money.
How to use this raised bed soil calculator
Use the bed’s interior dimensions. Enter the number of matching beds and the volume printed on your soil bags.
How the calculation works
Soil per bed = inside length × inside width × fill depth in cubic feet.
Multiply by the number of matching beds, then apply the optional allowance. Divide by 27 for cubic yards.
Bag count = total adjusted cubic feet ÷ listed volume per bag, rounded up.
Worked example
Two beds measuring 4 × 8 × 1 ft inside need 32 cu ft each and 64 cu ft total with no extra allowance. That is 2.37 cu yd, or 32 bags when each bag contains 2 cu ft.
Limits and assumptions
This is a volume estimate. Bagged mix may settle, and an actual bed can contain drainage or fill layers. Measure only the soil depth you intend to fill.
Frequently asked questions
Should I use outside or inside measurements?
Use inside measurements. The bed boards occupy space and should not be included in the soil volume.
Why is the bag count rounded up?
Stores sell whole bags. Any fractional bag requirement needs one more bag to cover the calculated volume.
What if my beds have different sizes?
Calculate each size separately. The matching-bed count applies only to beds with the dimensions currently entered.