Short answer: Use the inside length and width and only the soil depth still to add. Subtract a planned unfilled top gap and reasonably measured existing fill before rounding bags or bulk.
Swipe the diagram sideways to see every label. The full calculation is written below it.
Measure inside dimensions
Use the usable interior length and width, not the outside size of the boards. Multiply by the intended soil depth. If the bed has a tapered or irregular shape, divide it into simpler sections.
Convert to a purchase
For measurements in feet, length × width × depth gives cubic feet. Divide by 27 for cubic yards. If depth is in inches, use area in square feet × depth in inches ÷ 324. Round up only after choosing bag size or supplier bulk increments.
Account for what is already in the bed
Existing soil or other fill reduces the space left to fill. The raised-bed fill planner subtracts a level existing fill depth and an unfilled top gap. Irregular logs or tapered sides need a separate volume estimate. Confirm the growing mix with a supplier for what you intend to plant.
Hypothetical worked example
A raised bed with an 8 × 4 ft inside footprint filled 10 inches deep needs 8 × 4 × 10 ÷ 324 = 0.99 cubic yards before any settling allowance. Measure inside dimensions rather than the outside of thick boards.
Which situation matches your project?
Limit to check: Volume determines quantity, not soil composition. Confirm a growing mix appropriate for the intended plants.
Measuring at the site? The guided field workflow records outlines and cutouts, checks their placement, and makes a printable sheet before you choose materials.
Try the focused calculation
Further reading
YardSetup prepared this guide from the stated geometry and the linked references where provided. The adjustable example runs in your browser. See our formulas and limits or report an error.