Calculate the soil volume your bed needs
Measure the inside of a rectangular or circular bed and enter the depth you still need to fill. This soil calculator reports the measured volume, order volume with your chosen allowance, whole-bag count and estimated bag purchase cost. It converts between m³, liters, ft³ and yd³.
Our raised-bed soil planning guide explains how to avoid outside-measurement errors, handle partially filled beds and round a complete order to whole bags.
Formulas
- Rectangular bed: volume = inside length × inside width × fill depth.
- Circular bed: volume = π × (inside diameter ÷ 2)² × fill depth.
- Several identical beds: multiply the single-bed volume by the bed count.
- Order volume: measured volume × (1 + chosen allowance ÷ 100).
- Whole bags: round order volume divided by bag volume upward.
Metric length and width are entered in meters, depth in centimeters and bag volume in liters. Imperial length and width use feet, depth uses inches and bags use cubic feet. Switching unit systems converts the entered measurements rather than silently interpreting the same numbers as new units.
Worked example
A bed measuring 2 m by 1 m with a 30 cm fill depth needs 0.6 m³, or 600 liters. With 40-liter bags and no extra allowance, it needs 15 bags. If you choose 10% extra, the planning amount is 660 liters and rounds up to 17 bags. At 8 currency units per bag, the bag purchase cost is 136.
Assumptions to check
The bed is treated as having a uniform fill depth. Extra allowance defaults to zero because compaction or settling is not represented by one universal percentage. Enter a bag’s volume, not its mass. The cost field uses your own currency consistently and excludes delivery, tax and bulk-price differences.
This is a quantity calculator, not a soil recipe or fertilizer recommendation. For irregular spaces, calculate simpler sections separately and combine their volumes before rounding an order.
Plan the next step
Once the bed is filled, explore planting layout with the Seed Calculator. Both tools sit in the Biology category, alongside the separate pet-calculator collection.
Frequently asked questions
Should I measure outside the bed walls?
Use inside dimensions and only the depth still needing fill. Wall thickness and existing material reduce the space to fill.
Why are bags rounded upward?
Bags are purchased whole. The calculator divides total order volume by bag volume and rounds the final count upward.
Does every order need ten percent extra?
No. Extra allowance defaults to zero and is your own planning choice, not a universal settling or compaction rate.