Raised Bed Soil Calculator
Enter your bed's dimensions and fill depth to get cubic feet, cubic yards for bulk orders, and bag counts.
| Bag size | Bags needed |
|---|---|
| 1.5 cu ft bags | 22 |
| 2 cu ft bags | 16 |
Bulk soil usually beats bags once you're around a cubic yard or more. Plan to mix in 20 to 30% compost, and expect the fill to settle a few inches over the first season.
How it works
Enter your bed's length, width, and how deep you want to fill it, and the calculator multiplies the three to get cubic feet, then converts that into cubic yards for bulk delivery quotes and into bag counts for the two most common bag sizes sold at garden centers.
Worked example: an 8 by 4 foot bed filled 12 inches (1 foot) deep needs 8 times 4 times 1, which is 32 cubic feet. That works out to 1.19 cubic yards if you're ordering bulk soil by the yard. In bags, that's 22 bags at 1.5 cubic feet each, or 16 bags at 2 cubic feet each, so buying the larger bag size means fewer trips to load and unload.
A quick rule of thumb: once you need somewhere around a cubic yard or more, bulk delivery is usually cheaper per cubic foot and a lot less carrying, even accounting for a delivery fee. Below that, bagged soil is often simpler if you don't have anywhere to dump a loose pile.
FAQ
Should I fill the whole bed with bagged garden soil?
Most gardeners mix in 20 to 30% compost with a bagged or bulk garden soil or topsoil base rather than using compost alone, which tends to hold too much water and compact over time. A blend gives roots both structure and nutrients.
Why does my bed need more soil next spring?
Soil settles a few inches over the first season as organic matter breaks down and air pockets compress, especially in a brand-new bed. Plan to top off with an inch or two each spring rather than assuming one fill lasts forever.
How deep does my bed actually need to be?
Six inches works for shallow-rooted crops like lettuce and herbs, 12 inches covers most vegetables including tomatoes and peppers, and 18 inches gives root crops like carrots and potatoes room to size up without hitting the bottom of the bed.
Do I need to account for the existing ground underneath?
If your bed sits on decent native soil without a hardpan or heavy clay layer close to the surface, roots will often work down past what you filled, so you don't always need to fill every inch. If you're on a patio, gravel, or poor subsoil, fill the full depth.
For what to actually put in the bed, see what to fill a raised garden bed with and the best soil mix for a vegetable garden. If you're still deciding on depth, see how deep should a raised garden bed be.