Enter the size of your raised bed, how deep the soil will be and how many beds you have. The calculator shows how much soil to buy, and how much of each ingredient for the mix you choose.
Extra for settling and cost
What to buy for this mix
Bag sizes vary by brand. Check the volume printed on the bag.
How to measure a raised bed
- Measure the inside length and width of the bed, not the outside of the boards.
- For depth, use how deep the soil will be. Most people leave an inch or two below the top edge so water doesn’t run over.
- If you have several beds the same size, enter the number of beds. For beds of different sizes, work each one out separately.
Soil needed for common bed sizes
| Bed size (inside) | Soil depth | Cubic feet | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|---|
| 4 ft × 4 ft | 12 in | 16 | 0.59 | 11 |
| 3 ft × 6 ft | 12 in | 18 | 0.67 | 12 |
| 4 ft × 8 ft | 6 in | 16 | 0.59 | 11 |
| 4 ft × 8 ft | 12 in | 32 | 1.19 | 22 |
| 4 ft × 8 ft | 18 in | 48 | 1.78 | 32 |
These figures have no extra added. New beds settle, so add about 10 percent, which the calculator does for you.
Choosing a soil mix
The calculator offers three common options and shows how much of each ingredient to buy.
- 60% topsoil, 40% compost: a sturdy, affordable mix that holds water well. A good choice for large or deep beds.
- Equal thirds of compost, peat moss or coco coir, and vermiculite: a light, loose mix popular for square-foot gardening. It drains well but costs more to fill a big bed.
- Bagged raised bed soil only: the simplest option for one or two small beds.
Topsoil on its own isn’t a good fill for raised beds. It packs down hard and drains poorly without organic matter mixed in.
Worked example
Two 4 ft × 8 ft beds, soil 12 inches deep, with the 60/40 mix:
- 4 × 8 × 1 = 32 cubic feet per bed, 64 cubic feet for two
- With 10 percent extra for settling: 70.4 cubic feet, or 2.61 cubic yards
- Topsoil (60%): 1.56 cubic yards, about 42 cubic feet
- Compost (40%): 1.04 cubic yards, about 28 cubic feet
- If you bought bagged soil instead: 47 bags of 1.5 cubic feet
Saving soil in deep beds
Beds 18 inches or deeper take a lot of soil. Some gardeners fill the bottom third with logs, branches or leaves, which slowly break down, and put soil on top. It saves money, but expect the soil to sink more over the first year or two and top it up with compost.
Frequently asked questions
How much soil do I need for a 4 × 8 raised bed?
At 12 inches deep, a 4 ft × 8 ft bed holds 32 cubic feet, which is about 1.2 cubic yards or 22 bags of 1.5 cubic feet. Add about 10 percent for settling.
How deep should a raised bed be?
At least 6 inches for shallow-rooted crops like lettuce. About 12 inches suits most vegetables, and deeper beds are easier on your back.
How many bags of soil make a cubic yard?
18 bags of 1.5 cubic feet, or 27 bags of 1 cubic foot.
Can I fill a raised bed with just topsoil?
It’s better not to. Topsoil alone compacts and drains slowly. Mix in plenty of compost, or use one of the mixes in the calculator.
Why did the soil in my raised bed sink?
New soil settles as it’s watered, and organic matter breaks down over time. Topping up with an inch or two of compost each year keeps the bed full.
Results are estimates for planning. Bag sizes vary by brand. See How We Calculate for the formulas and values we use.