Raised Bed Soil Calculator
How much soil to fill a raised garden bed
Filling a raised garden bed? Enter the bed length, width and height (as the depth) to get the soil needed in cubic feet, cubic yards and bags.
The best raised-bed mix
A popular blend is roughly ⅓ topsoil, ⅓ compost, ⅓ aeration (peat or coco coir) — sometimes called "Mel's Mix." Enter the bed's inside height as the depth. Beds settle over the first season, so fill right to the top.
How deep do roots need?
Most vegetables thrive in 10–12 inches of soil; deep-rooted crops like tomatoes and carrots appreciate more. If your bed sits on open ground, roots can reach into the soil below it; if it's on a hard surface like a deck or patio, give the full depth.
Filling a deep bed economically
For tall beds you don't need premium mix all the way down. Fill the bottom third with cheaper material — coarse compost, untreated logs, leaves or fill dirt — and reserve the quality growing mix for the top 10–12 inches where roots feed.
Raised Bed Soil Calculator: frequently asked questions
How much soil for a 4x8 raised bed?
A 4×8 ft bed 12 inches deep needs about 32 cubic feet (≈1.2 cubic yards).
Can I just use topsoil in a raised bed?
Mix topsoil with compost and an aerator — pure topsoil compacts and drains poorly.
Should I put anything in the bottom of a raised bed?
On open soil, just loosen the ground and optionally lay cardboard to smother grass. For deep beds, filling the lower portion with logs and leaves (a method called hügelkultur) saves mix and feeds the bed as it breaks down.