Raised Bed Soil Calculator
Find how much soil fills your raised bed, in bags or cubic yards, and what to mix.
Measure your project
Your answer
That covers 32 sq ft. We added 10% extra.
If you buy bags
What it costs
$18.99 for a 2 cubic foot bag at one store (Oct 2026). Raised bed soil prices vary a lot, so check yours.
Quick answers
- How deep?
- 6–12 in for most vegetables, says Utah State. We start at 12 in.
- A 4 × 8 ft bed, 12 in deep
- 32 cubic feet before extra: 16 bags of 2 cubic feet, or 25 of 1.3. With 10%, it is 18 or 28.
- What mix?
- Compost and topsoil, 1:2 or 1:1 (Maryland). Iowa State and Utah State also give equal-parts mixes.
- Bags in a cubic yard
- 13.5 bags of 2 cubic feet. That is 27 cubic feet in all.
How to work it out
- Measure the inside length and width of the bed in feet.
- Turn the depth into feet: inches ÷ 12.
- Multiply the three numbers together. That gives cubic feet.
- The calculator starts with 10% extra, so add that too.
- Divide the cubic feet by the bag size. Round up. Cubic feet ÷ 27 gives cubic yards.
4 × 8 × 1 = 32 cubic feet
32 + 10% = 35.2 cubic feet
35.2 ÷ 2 = 17.6, so 18 bags of 2 cubic feet
35.2 ÷ 27 = 1.30 cubic yards
How deep to make the bed
Utah State University Extension says a bed should be at least 6–12 in high. That leaves room for the roots of most vegetables.
Rutgers goes further. It suggests at least 12 in of bought-in topsoil.
Is your bed on a patio or other hard ground? Then roots can't grow down past it. For that case, Maryland Extension says 8 in for leafy greens, beans and cucumbers. Peppers, tomatoes and squash need 12–24 in.
The calculator starts at 12 in. That is the top of Utah State's range and the Rutgers minimum.
What to fill it with
You can buy bags of raised bed mix, or mix your own. Extension services give a few recipes.
- Maryland: compost and topsoil, 1:2 or 1:1.
- Iowa State: about 70% topsoil and 30% compost.
- Iowa State: equal parts topsoil, organic matter and coarse sand.
- Utah State: equal parts compost, topsoil and a drainage material.
Maryland also says 25–50% of the bed, by volume, should be organic matter, like compost.
Our “⅔ topsoil + ⅓ compost” choice is Maryland's 1:2 mix. It is close to Iowa State's 70/30.
| Mix | Topsoil | Compost | Coarse sand |
|---|---|---|---|
| ⅔ topsoil + ⅓ compost | 21.3 | 10.7 | – |
| Equal parts topsoil, compost, coarse sand | 10.7 | 10.7 | 10.7 |
Pick a mix in step 1, and the answer splits it for you.
Bags for common bed sizes
Each bed below is 12 in deep, with no extra.
| Bed | Cubic feet | 2 cu ft bags | 1.3 cu ft bags |
|---|---|---|---|
| 2 × 4 ft | 8 | 4 | 7 |
| 4 × 4 ft | 16 | 8 | 13 |
| 3 × 6 ft | 18 | 9 | 14 |
| 2 × 8 ft | 16 | 8 | 13 |
| 4 × 8 ft | 32 | 16 | 25 |
| 4 × 12 ft | 48 | 24 | 37 |
Kellogg's own label fits these sums: 4 sq ft per bag at 6 in.
What bags cost
We found only 3 store prices, so treat them as rough.
- 1.3 cubic foot bag: $14.99 in Connecticut.
- 2 cubic foot bag: $18.99 in Oregon.
- 2 cubic foot bag: $15.20 in California (list price).
That is $7.60 to $11.53 per cubic foot. Before extra, a 4 × 8 ft bed, 12 in deep, comes to about $243–$304 in 2 cubic foot bags. In 1.3 cubic foot bags, it is about $375.
For a home-made mix, our middle bulk topsoil price is $40 a cubic yard, from 13 sellers. We have no compost price we trust yet.
Will the soil sink?
Rutgers says soils made with topsoil settle once. After that, they tend to keep their volume. It gives no figure for how much.
The 10% in step 1 is borrowed from one topsoil seller. Rutgers gives no number for raised beds, so pick 0% if you like.
Questions people ask
How much soil do I need for a raised bed?
Multiply length × width × depth, all in feet, for cubic feet. A 4 × 8 ft bed, 12 in deep, holds 32 cubic feet.
How many bags of soil do I need for a 4 × 8 raised bed?
At 12 in deep, 16 bags of 2 cubic feet before extra, or 18 with 10%. In 1.3 cubic foot bags, it takes 25, or 28.
How many inches of soil for a raised garden bed?
Utah State says 6–12 in for most vegetables. Rutgers says at least 12 in of topsoil. On hard ground, Maryland says 12–24 in for tomatoes.
What is the best soil mix for a raised bed?
Maryland Extension mixes compost and topsoil 1:2 or 1:1. Iowa State suggests about 70% topsoil and 30% compost.
What does raised bed soil mean?
It is the soil that fills a raised bed. Stores sell it in bags, often called raised bed mix. You can also mix topsoil and compost yourself.
How do I work out raised bed soil in cubic yards?
Find the cubic feet, then divide by 27. A 4 × 8 ft bed, 12 in deep, holds 1.19 cubic yards before extra.
Will raised bed soil sink?
Rutgers says soil made with topsoil settles once, then tends to keep its volume. It gives no figure for how much, so top it up if it drops.
How much does one bag of raised bed soil fill?
Kellogg says a 2 cubic foot bag fills 4 sq ft about 6 in deep. At 12 in deep, it fills 2 sq ft.
Where our numbers come from
- Raised bed depth: Utah State University Extension
- Raised bed soil: University of Maryland Extension
- Raised bed soil: Rutgers fact sheet FS1328
- Raised bed mix: Iowa State Extension
- Raised bed mix bags: Kellogg Garden Organics (2 cubic feet)
- Raised bed soil prices: 3 US stores (Oct 2026; few prices)
- Topsoil prices: the middle price of 13 yards (bulk) and 2 stores (bags), Oct 2026
- Topsoil extra: Palmetto Sand & Gravel (add 10% for settling)
Made by BuildersCount. Last checked 3 Oct 2026.
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