Guide & tool
How much soil does a raised bed need?
Enter the bed. The answer is below it — cubic feet, cubic yards, and how many bags that actually is. No sign-up, and nothing withheld.
Pick the depth before you price the soil.
Depth drives everything — the volume, the cost, what you can grow, and how often you water. It is the decision worth spending a minute on.
- 6 inches
- Lettuce, spinach, herbs, radishes. Shallow roots only, and it dries out fast in an Alabama summer.
- 10–12 inches
- The honest default. Tomatoes, peppers, squash, beans, most of what people actually plant.
- 18 inches
- Carrots, parsnips, potatoes — anything that goes down rather than up. Also the depth that stops you watering twice a day in July.
- 24 inches
- Standing-height beds and poor-drainage sites, where the bed has to be its own soil profile.
The questions that follow.
- How much soil do I need for a 4x8 raised bed?
- A 4 by 8 foot bed filled 12 inches deep holds 32 cubic feet, which is about 1.19 cubic yards, or roughly 43 standard 0.75 cubic foot bags. At 18 inches deep the same bed takes 48 cubic feet, about 1.78 cubic yards.
- Is it cheaper to buy soil in bags or in bulk?
- Bags stop making sense somewhere around one cubic yard. A cubic yard is 27 cubic feet, which is 36 standard bags, and hauling and opening 36 bags costs more in time and money than a delivered load. Below about half a yard, bags are usually simpler.
- What should raised-bed soil actually be?
- A workable mix is roughly half topsoil or garden soil, a third finished compost, and the rest something that keeps it open — pine bark fines, coarse sand, or perlite. Straight bagged potting mix is expensive at bed volume and straight topsoil compacts. The proportions matter less than making sure it drains and has real organic matter in it.
- Do I have to fill the whole bed with soil?
- No, and for a deep bed you should not. Below about 12 inches most vegetable roots are not working, so the bottom of an 18 or 24 inch bed can be filled with coarse organic material — branches, logs, leaves — which settles over time and saves a real amount of soil. Calculate the full volume first, then decide how much of the bottom to fill with something other than soil.
- How much will the soil settle?
- Expect a few inches in the first season, more if the mix is compost-heavy or the bottom was filled with wood. Plan to top it up the following spring. That is normal and not a sign the bed was built wrong.
Central & East Alabama
Or skip the arithmetic and the hauling.
We build raised beds and full garden systems and quote the soil with them — build only, build and fill, or built, filled and planted. Every job is quoted on the actual property, so there is no package to fit yourself into.Serving Tallapoosa, Lee, Macon, Chilton, Shelby, Elmore, and Jefferson counties, Alabama.