Soil for a 4x8 Raised Bed 18 Inches Deep
A raised bed 4 by 8 feet and 18 inches tall holds 48.0 cubic feet. How much soil for a 4x8 raised bed 18 inches deep in bags: 24 two-cubic-foot bags. In bulk: about 1.78 cubic yards.
Volume and tonnage calculator →The math
- Volume: 4 × 8 × (18 ÷ 12) = 48.0 cu ft.
- Cubic yards: 48.0 ÷ 27 = 1.78 yd³.
- Bags: 48.0 ÷ 2 = 24 bags (2 cu ft), or ÷ 1.5 = 32 bags (1.5 cu ft).
The topsoil calculator handles any bed size.
Related: Soil for a 4x8 Raised Bed 6 Inches Deep
Soil for a 4x8 bed at other depths
| Depth | Cubic feet | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 6 in | 16.0 | 0.59 | 8 |
| 8 in | 21.3 | 0.79 | 11 |
| 10 in | 26.7 | 0.99 | 14 |
| 12 in | 32.0 | 1.19 | 16 |
| 18 in | 48.0 | 1.78 | 24 |
| 24 in | 64.0 | 2.37 | 32 |
When bulk soil pays off
This bed is big enough that a bulk load of garden mix usually beats bags. Many yards sell a blended raised-bed mix of topsoil and compost by the yard.
Related: Soil for a 4x8 Raised Bed 8 Inches Deep
What to fill it with
Many gardeners blend topsoil with compost, around 50 to 60 percent topsoil. The compost adds nutrients and keeps the mix loose. Bagged potting soil alone is light and can dry out fast in a deep bed.
Settling
New soil settles, often by 10 to 20 percent in the first season. Overfill slightly or plan to top up with compost next spring. In very deep beds, the bottom few inches can be coarse material, since most vegetable roots work the top 12 inches.
Checking quality
Squeeze a handful: quality topsoil holds together loosely and breaks apart, rather than forming a sticky ball of clay or falling apart like sand. Avoid soil that smells sour or contains debris.
Measuring accurately
Measure each bed or area in feet and multiply length by width for square feet. For curved beds, a rough rectangle around the shape overestimates; split it into smaller shapes instead. Measure the depth you actually want to add, not the total depth of the bed if some soil is already there.
Questions people ask
How many bags of soil for a 4x8 raised bed?
About 24 bags of 2 cubic feet at 18 inches deep.
How many cubic feet in a 4x8x18 inch bed?
48.0 cubic feet.
How many yards of soil for a 4x8 raised bed?
About 1.78 cubic yards at 18 inches deep.
What soil mix is best for raised beds?
Topsoil blended with compost, roughly 60/40, is a common starting point.
Will raised bed soil settle?
Yes, often 10 to 20 percent in the first season.
Related guides
- How Much Does a Yard of Topsoil Cover?
- How Many Bags of Topsoil in a Yard? Size Chart
- Fill Dirt vs Topsoil: Differences, Uses and Tons to Order
- How Much Does a Yard of Dirt Weigh? Topsoil, Fill, Clay
- Soil for a 4x8 Raised Bed 11 Inches Deep
- Soil for a 4x8 Raised Bed 12 Inches Deep
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