Raised Bed Soil Calculator – How Much Do I Need? | CalcLoft
Find out exactly how much soil your raised bed needs — in cubic feet, cubic yards and bags — for any bed size and depth.
How to calculate soil for a raised bed
A raised bed is a simple box, so you only need three measurements: the length, the width and how deep you want the soil. Multiply them together to get the volume in cubic feet:
Bed volume = length (ft) × width (ft) × (height in inches ÷ 12)
For example, a 4 × 8 ft bed filled 12 inches deep holds 4 × 8 × 1 = 32 cubic feet of soil. One cubic yard equals 27 cubic feet, so that is about 1.2 cubic yards. Bags of garden soil are usually sold in 1.5 or 2 cubic foot sizes, so divide the volume by the bag size and round up.
How much soil for a 4 × 8 ft raised bed?
The table below shows what a standard 4 × 8 ft raised garden bed needs at each common fill height. Bags are rounded up, and the mix will settle 10–15% after the first few waterings.
| Bed height | Soil volume | Cubic yards | 2-cu-ft bags | 1.5-cu-ft bags |
|---|---|---|---|---|
| 6 in | 16 cu ft | 0.6 cu yd | 8 bags | 11 bags |
| 12 in | 32 cu ft | 1.2 cu yd | 16 bags | 22 bags |
| 18 in | 48 cu ft | 1.8 cu yd | 24 bags | 32 bags |
| 24 in | 64 cu ft | 2.4 cu yd | 32 bags | 43 bags |
How much soil does a raised bed need?
There is no single answer — it depends on the footprint and depth of your bed. A shallow 4 × 8 ft bed at 6 inches needs only 16 cubic feet (about 8 bags of 2 cu ft), while the same bed at 24 inches needs 64 cubic feet (about 32 bags). Taller beds hold more soil for deep-rooted plants, but they cost more to fill. Use the calculator above to check your exact size, and buy roughly 10–15% extra because fresh soil settles after it is watered.
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Raised bed soil calculator FAQ
How much soil do I need for a 4×8 raised bed?
A 4 × 8 ft raised bed needs 16 cubic feet at 6 inches deep, 32 cubic feet at 12 inches, 48 cubic feet at 18 inches and 64 cubic feet at 24 inches. At the most common 12-inch depth that is about 1.2 cubic yards or 16 bags of 2-cu-ft soil.
How deep should my raised bed be?
6 inches suits shallow-rooted greens, lettuce and herbs. 12 inches is the sweet spot for most vegetables. Go 18–24 inches for root crops, potatoes and tall, trellised tomatoes, or for gardeners who prefer not to bend. Remember: every extra inch of depth means more soil to buy and more weight on the ground below.
Should I buy extra soil?
Yes — fresh soil and compost mixes settle 10–15% after the first waterings. Buy about 15% extra up front, or plan to top the bed off with a bag or two after a few weeks.
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