Raised Bed Soil Calculator

It multiplies length by width by depth, converting the depth from inches to feet first (depth divided by 12), then multiplies by the number of beds. So an 8 by 4 ft bed filled 12 inches deep is 8 x 4 x 1 = 32 cubic feet per bed.

Most vegetables thrive in 10 to 12 inches of soil, which gives roots room and holds moisture between waterings. Deep-rooted crops such as carrots, parsnips and tomatoes do better toward the full 12 inches or more.

There are 27 cubic feet in a cubic yard. Bulk soil and compost are usually sold by the cubic yard, so the calculator shows that figure to help you order a delivery instead of counting bags.

Soil is sold by the whole bag, so any partial need is rounded up to the next full bag. A 32 cubic foot bed at 1.5 cubic feet per bag needs 21.33 bags of material, which rounds up to 22. The small surplus is handy for topping up later.

Yes. The Bag size field defaults to 1.5 cubic feet, a common bagged-soil volume, but you can set it to 1, 2, 3 or any size your supplier sells. Set it to 0 and the tool skips the bag count and shows only the volume.

Leave an inch or two below the rim so water and mulch do not spill over the edge. Fresh soil and compost also settle after the first few waterings, so plan to add a little more in the opening season.

A popular blend is roughly one third compost, one third topsoil and one third an aeration material such as coarse sand or perlite. Adjust the ratio to suit your plants and your local ground conditions.

Use the inside dimensions of the frame, the actual space that holds soil. Measuring the outer edge of the boards overstates the fill volume by the thickness of the timber on each side.

No. The whole estimate is computed in your browser as you type, and nothing you enter is uploaded to a server, so it works offline once the page has loaded.