Landscaping calculator
Soil calculator
Size the bed, pick the mix, and get the soil volume in cubic feet, cubic yards and bags, split into the topsoil, compost and aeration components of a proper raised bed blend.
Your project
Raised beds are typically 10-18" deep. Fill to about 2" below the rim.
Crews typically order 5-10% extra to cover compaction, spillage and uneven subgrade.
Soil needed
504
cubic feet
- Volume in cubic yards
- 18.67 cu yd
- Area per bed
- 480 sq ft
- 1.5 cu ft bags
- 336 bags
- Approximate weight
- 27,720 lb
- Topsoil component (60%)
- 302.4 cu ft
- Compost component (30%)
- 151.2 cu ft
- Aeration component (10%)
- 50.4 cu ft
- Estimated cost
- $1,120
The 60/30/10 split is the standard raised bed recipe: screened topsoil for body, finished compost for fertility, and perlite, pumice or coarse bark for drainage. Buy them separately and blend on a tarp if the pre-mix is priced above $70 a yard.
The shareable link reopens this calculator with your exact inputs.
How to calculate soil for a raised bed
Length times width times depth, all in feet, gives cubic feet directly. A 4 ft by 8 ft bed filled 12 inches deep is 4 x 8 x 1 = 32 cubic feet, which is 1.19 cubic yards or 22 bags of 1.5 cubic feet.
Fill to about two inches below the rim rather than level with it. Soil mounds when you water it in, and the gap gives you room to top up with compost each spring without spilling over the sides.
If the bed sits on open ground rather than a hard surface, you can fill the bottom third with coarse organic material — branches, leaves, old straw. That hugelkultur layer cuts the purchased soil by a quarter, though it will settle noticeably in year one.
What to actually put in the bed
Straight topsoil compacts and drains poorly in a confined box. Straight compost is too rich, holds too much water and slumps by half within a season. The blend that works is roughly 60% screened topsoil, 30% finished compost and 10% aeration material.
Bagged potting mix is engineered for containers, not beds. It is peat-heavy, expensive, and dries out fast in a volume that big. Save it for pots under about three cubic feet.
Expect to add one to two inches of compost annually. Organic matter burns off, and beds drop roughly an inch a year as the coarse fraction breaks down.
Soil volume for common raised bed sizes
Cubic feet and bags at 12 inches deep, using 1.5 cu ft bags.
| Bed size | Cubic feet | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|
| 2 ft x 4 ft | 8 | 0.3 | 6 |
| 3 ft x 6 ft | 18 | 0.67 | 12 |
| 4 ft x 4 ft | 16 | 0.59 | 11 |
| 4 ft x 8 ft | 32 | 1.19 | 22 |
| 4 ft x 12 ft | 48 | 1.78 | 32 |
| 5 ft x 10 ft | 50 | 1.85 | 34 |
Frequently asked questions
+How much soil do I need for a 4x8 raised bed?
32 cubic feet at 12 inches deep — 1.19 cubic yards, or 22 bags of 1.5 cubic feet. At 6 inches deep it halves to 16 cubic feet.
+How many bags of soil make a cubic yard?
Eighteen bags at 1.5 cubic feet, 27 bags at 1 cubic foot, or 13.5 bags at 2 cubic feet. Bulk delivery beats bags on price at roughly one cubic yard.
+What is the best soil mix for raised beds?
About 60% screened topsoil, 30% finished compost and 10% aeration material such as perlite, pumice or coarse bark fines. That gives structure, fertility and drainage in a box where roots cannot escape downward.
+How deep should a raised bed be?
Ten to twelve inches suits most vegetables. Root crops such as carrots and parsnips want at least twelve; tomatoes and squash are happier with eighteen if the bed sits on a hard surface with nothing to root into below.
+Can I use garden soil in a raised bed?
Bagged garden soil is formulated for in-ground beds and packs down hard in a raised box. Use it as part of the mix, not all of it, and always cut it with compost and an aeration material.
+Why does the soil level in my raised bed drop every year?
Organic matter decomposes. A bed loses roughly an inch a year, more in the first season as the initial mix settles. Top up with compost each spring rather than replacing the whole bed.