What does this soil calculator calculate?
This calculator estimates the volume needed to fill a rectangular growing area. It multiplies length by width by fill depth, then converts the result into cubic yards and your selected bag size.
What you will need
Length and width
Measure the inside dimensions of the bed. Using the outside dimensions can slightly overstate the amount of soil you need when the bed has thick sides.
Fill depth
Measure only the empty depth that you plan to fill. If the bed already contains soil, do not enter the total wall height.
How the calculation works
For an 8 foot by 4 foot bed with a 12 inch fill depth, the calculation is 8 × 4 × 1 = 32 cubic feet. There are 27 cubic feet in one cubic yard, so 32 cubic feet is about 1.19 cubic yards.
Important assumptions
- The growing area is rectangular.
- Depth is treated as an average across the bed.
- The estimate does not account for settling after watering.
- Bag volume matches the amount printed on the package.
Common measuring mistakes
The most common mistake is entering the full bed height when only a partial refill is needed. Sloped ground and uneven existing soil can also change the actual volume. Measure several points and use an average depth when the base is uneven.