How to use this calculator
Measure between the inside faces of one bed, choose the depth of new soil you actually need to add, and enter how many identical beds you are filling. If a bed already contains soil or a base layer, enter only its remaining fill depth. The sleeper cut planner can carry its inside footprint and bed count here; you still need to enter fill depth and your supplier’s bag volume.
The formula
A worked example
An 8 × 4 ft bed filled 12 inches deep takes 32 cubic feet, or 1.19 cubic yards. With no extra allowance and 1.5 cubic-foot bags, buy 22 bags, leaving 1 cubic foot against the plan. Three beds each measuring 2.2 × 1 m inside with 30 cm of new fill need 1,980 L in total. With no extra allowance and 40 L bags, buy 50 bags and retain 20 L. Rounding each bed separately would instead buy 51 bags.
Assumptions & limitations
All counted beds have the same rectangular inside footprint and uniform fill depth, and use the same material. Settling and compaction are represented only by your extra allowance. Leftover is the difference from the planned volume, not a guarantee of real-world yield. For different bed sizes or fill depths, calculate their volumes separately and combine those volumes before rounding a bag order. This estimates volume, not a soil blend, plant-specific growing depth or structural design.
Common questions
Should I use outside dimensions?
No. Wall thickness occupies space, so use the interior length and width.
Can I calculate only a top-up?
Yes. Enter the thickness of new soil you want to add instead of the full bed height.
How do I order bags for several raised beds?
For identical beds, enter their count and round only the combined order up to whole bags. Do not multiply a rounded per-bed bag count, because bags can be shared between beds.
Does the sleeper planner set my fill depth?
No. It transfers only the inside footprint and number of beds. Existing soil, a base layer and the space left below the rim change the depth of new material needed.
Units reference
The calculation follows the method above. This reference supports the units and conversions.
NIST: units and conversion factors ↗Formula and worked example checked against automated test cases. About our methodology.