MEASURE ONCE. CALCULATE CLEARLY.
How to calculate how much soil you need
Measure the usable inside length and width of the growing space, then measure the depth you intend to fill. Use the actual empty volume you need to add: an existing soil layer reduces the remaining depth.
- 01
Measure the inside length and width of the rectangular space.
- 02
Measure the depth that still needs to be filled.
- 03
Enter each value and select its unit. Mixed units are converted automatically.
- 04
Choose a bag size and optional buffer if you are planning a purchase.
The soil volume formula
All three measurements must use compatible units before they are multiplied. The calculator normalizes them internally, calculates with full precision and rounds only the numbers shown on screen.
Example calculation
1 Convert 12 inches to 1 foot.
2 8 × 4 × 1 = 32 cubic feet.
3 32 ÷ 27 ≈ 1.19 cubic yards.
4 32 × 28.316846592 ≈ 906 liters.
How many bags of soil do I need?
Divide the required volume by the volume printed on one bag. Bag sizes are not universal, so the presets are only shortcuts. Select liters or cubic feet and use Custom when your product is a different size.
Purchase quantities always round up to a whole bag. For example, 22.1 bags becomes 23 bags because 22 bags would provide less than the calculated volume.
Should I buy extra soil?
A buffer can account for small measurement differences, settling and minor losses. It remains optional because the right allowance varies. The result separates the required geometric volume from the buffered purchase volume, so you can compare both.
Cubic feet, cubic yards and liters explained
Cubic feet and liters are convenient for smaller quantities and bagged products. Cubic yards and cubic meters make larger bulk volumes easier to read. These units describe the same volume.
Common soil calculation mistakes
- Multiplying feet by inches without converting one of them first.
- Measuring outside dimensions instead of the usable inside space.
- Using the full bed height when some soil is already present.
- Rounding each conversion before the final calculation.
- Treating an irregular or tapered container as a precise rectangle.
Frequently asked questions
How do I calculate soil for a raised bed?
Measure the usable inside length, width and fill depth. Convert the measurements to compatible units, then multiply length × width × depth. The calculator handles those conversions for rectangular beds.
How many cubic feet are in a cubic yard?
One cubic yard contains exactly 27 cubic feet. Divide cubic feet by 27 to convert a soil volume to cubic yards.
How many liters are in a cubic foot?
One cubic foot is approximately 28.316846592 liters. Grownestia keeps that precision internally and rounds only the displayed estimate.
Should I buy extra soil?
That depends on the space and material. A small buffer may help with measurement variation, settling or small losses, but no single percentage suits every project. Choose 0%, 5%, 10% or your own value up to 50%.
Why does the calculator round soil bags up?
Bags are purchased as whole units. If the calculation gives 22.1 bags, buying 22 would be less than the calculated volume, so the purchasing estimate rounds up to 23.
Can I use this for planters?
Yes, when the planter can be reasonably treated as a rectangular space. For tapered, round or irregular containers, this rectangular calculation will only be a rough approximation.