How much soil for a 4×8 raised bed?
A 4 × 8 ft raised bed 12 inches tall, filled to 1 inch below the rim (11 inches deep), holds 29.3 cubic feet of soil (1.09 cubic yards). With 10% extra for settling, buy 32.3 cubic feet: 22 bags of 1.5 cu ft, or 17 bags of 2 cu ft. If yours is a "12 inch" wooden bed made of two 2×6 boards, it is really 11 inches tall, so the soil is 10 inches deep: 26.7 cubic feet, or 29.3 cubic feet with settling (20 bags of 1.5 cu ft).
How to work it out
- Soil depth: 12 in bed − 1 in below the rim = 11 in
- 8 ft × 4 ft × 11 in ÷ 12 = 29.3 cu ft (bed volume)
- 29.3 cu ft + 10% for settling = 32.3 cu ft
- 32.3 cu ft ÷ 1.5 cu ft per bag = 22 bags
The 4 × 8 is the most common raised bed because standard 8 ft boards frame it with almost no cutting, and at 4 ft wide you can reach the middle from either side (University of Missouri Extension calls four feet a convenient width). Two dozen 1.5 cu ft bags is a car-load or two; if you are filling two or more of these, a cubic yard or two of bulk garden blend usually costs much less.
Adjust for your project
More options: Settling · Mix · Bag price …
- Soil depth (filled)
- 11 in
- Soil to buy
- 32.3 cu ft (1.2 cu yd)
- Or order bulk garden blend
- 1.5 cubic yards
Bags for a 4×8 bed 12 in tall, by bag size
| Bag size | Bags to buy |
|---|---|
| 1 cu ft | 33 bags |
| 1.5 cu ft | 22 bags |
| 2 cu ft | 17 bags |
| 3 cu ft | 11 bags |
What to know about filling a 4×8 raised bed
Check the real height before you buy. A wooden bed sold or built as "12 inches" is usually two courses of 2×6 lumber, and a 2×6 is actually 5½ in tall, so the frame is 11 in. Enter 11 as the bed height; with an inch left below the rim for water and mulch, the soil is 10 in deep: about 27 cubic feet instead of the 32 a full 12 in would take. Put your own measurements into the calculator rather than the nominal size.
One cubic yard is 27 cubic feet, which is why "a yard per bed" is a common rule of thumb for 4 × 8s. With a settling allowance a true 12 in bed takes a bit more than that, so order a yard and a half if your supplier sells half-yards. Two beds take about 2.4 yards, which is where bulk delivery starts to beat a car full of bags clearly.
If you mix your own, the 60/30/10 split for this bed is worked out below, and University of Minnesota Extension’s advice to keep compost to a third or a half of the mix applies here too: a bed of pure compost stays wet and sinks.
Going taller? How much soil for a 4×8 raised bed 18 inches deep covers the extra 16 cubic feet. For a smaller starter bed, see How much soil for a 4×4 raised bed; for the metric version, How much soil for a 1.2 × 2.4 m raised bed. Converting a yardage into bags? How many bags of mulch are in a cubic yard has the same arithmetic for every bag size.
Different size? Use the full Raised Bed Soil Calculator.
What you’ll need
- Cedar raised bed kitMid-range price
Naturally rot-resistant wood, easy to extend or stack for depth. Expect the boards to weather gray.
See options on Amazon (opens in a new tab) - Garden dump cartMid-range price
Easier than a wheelbarrow for hauling bags and pots, and it tips to unload. Check the rated load against what you will carry.
See options on Amazon (opens in a new tab) - Coarse perliteBudget price
Lightweight mineral that keeps soil mixes open and draining.
See options on Amazon (opens in a new tab)
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Frequently asked questions
What is the 60/30/10 soil mix for a 4×8 bed 12 inches tall?
For 32.3 cubic feet including settling: 19.4 cu ft of topsoil (20 bags of 1 cu ft), 9.68 cu ft of compost (10 bags of 1 cu ft) and 3.23 cu ft of perlite (1 bag of 4 cu ft).
How much soil for two 4×8 raised beds 12 inches tall?
64.5 cubic feet with 10% for settling (2.39 cubic yards), or 44 bags of 1.5 cu ft. At that volume, compare a bulk delivery.
How many 2 cu ft bags fill a 4×8 raised bed?
17 bags of 2 cu ft for 32.3 cubic feet, which includes 10% for settling.
Other common sizes
- How much soil for a 4×8 raised bed 18 inches deep — 49.9 cu ft
- How much soil for a 4×4 raised bed — 16.1 cu ft
- How much soil for a 3×6 raised bed — 18.2 cu ft
- How much soil for a 2×8 raised bed — 16.1 cu ft
- How much soil for a 1.2 × 2.4 m raised bed — 871 L
Sources
- University of Minnesota Extension: Raised bed gardens (opens in a new tab) — Soil blend of roughly 1/2–2/3 topsoil and 1/3–1/2 plant-based compost; too much compost holds excess water.
- University of Missouri Extension: Raised-Bed Gardening (G6985) (opens in a new tab) — Four feet is a convenient width; about 3 ft if reached from one side; most plants need a 6–12 in rooting zone.
- Oregon State University Extension: Raised bed gardening (FS 270) (opens in a new tab) — Beds longer than about 6 ft should be reinforced so the soil doesn’t push the sides out.