Raised Bed Soil Calculator

Six inches handles shallow greens and herbs, but 10-12 inches suits most vegetables and root crops. Deep-rooted tomatoes and carrots appreciate 16-18 inches. If your bed sits on existing soil rather than a hard surface, roots will penetrate deeper than the bed walls, so 10-12 inches is usually enough for most crops.

Yes. The bottom several inches can be filled with coarse wood chips, branches, or straw (a hugelkultur-style base layer) that breaks down and feeds the soil over time while reducing the amount of premium mix you need at the top. If you do this, enter only the depth of the quality fill layer into the calculator.

Yes - expect 10-20% settling in the first season as compost and organic matter decompose. Fill beds slightly above the rim initially, and plan to top-dress with an inch or two of compost each spring to maintain productive depth. The settling is greatest in the first year and slows as the organic fraction stabilizes.

Bagged garden soil is screened topsoil with added compost and often some perlite - it is ready to use in beds without additional amendment. Bagged topsoil is more basic and benefits from compost additions. Neither is the same as potting mix, which is designed for containers and too light and fast-draining for use in raised beds without a larger proportion of topsoil.