Quick answer: A 4×4 raised bed needs 10.67 cubic feet at 8 inches deep or 16 cubic feet at 12 inches deep. For a 12-inch fill with 5% extra, plan for 16.8 cubic feet—about 0.62 cubic yard, 12 bags at 1.5 cu ft, or 9 bags at 2 cu ft.
4×4 raised-bed soil chart
These quantities assume a true 4×4-foot interior. “With 5% extra” is a purchasing allowance for minor measurement differences and settling—not another layer of soil.
| Fill depth | Exact volume | Cubic yards | With 5% extra |
|---|---|---|---|
| 6 inches | 8 cu ft | 0.30 cu yd | 8.4 cu ft |
| 8 inches | 10.67 cu ft | 0.40 cu yd | 11.2 cu ft |
| 10 inches | 13.33 cu ft | 0.49 cu yd | 14.0 cu ft |
| 12 inches | 16 cu ft | 0.59 cu yd | 16.8 cu ft |
| 18 inches | 24 cu ft | 0.89 cu yd | 25.2 cu ft |
| 24 inches | 32 cu ft | 1.19 cu yd | 33.6 cu ft |
How the 4×4 calculation works
Convert the fill depth to feet, then multiply the inside length, width and depth:
4 ft × 4 ft × depth in feet = cubic feet of soil
At 12 inches deep: 4 × 4 × 1 = 16 cubic feet.
For an 8-inch fill, divide 8 by 12 first. The calculation is 4 × 4 × 0.6667, or approximately 10.67 cubic feet. Divide cubic feet by 27 to convert the result to cubic yards.
How many bags fill a 4×4 raised bed?
The bag counts below include 5% extra and are rounded up to whole bags. Use the volume printed on the bag—not its weight—as the comparison number.
| Depth | 0.75 cu ft bags | 1 cu ft bags | 1.5 cu ft bags | 2 cu ft bags | 3 cu ft bags |
|---|---|---|---|---|---|
| 6 in | 12 | 9 | 6 | 5 | 3 |
| 8 in | 15 | 12 | 8 | 6 | 4 |
| 10 in | 19 | 14 | 10 | 7 | 5 |
| 12 in | 23 | 17 | 12 | 9 | 6 |
| 18 in | 34 | 26 | 17 | 13 | 9 |
| 24 in | 45 | 34 | 23 | 17 | 12 |
If you prefer no allowance, divide the exact volume in the first table by the bag size and round the final answer upward.
Choose the actual fill depth
Measure the soil depth you intend to add, not simply the height of the frame. Leaving one or two inches below the rim creates room for watering and mulch. For example, a 12-inch-tall frame filled to 10 inches should use the 10-inch row.
Six to eight inches may suit shallow-rooted plants when roots can continue into healthy ground below. Ten to twelve inches gives many vegetables more room. Beds over concrete, compacted soil or a solid base must supply the complete root zone and may need greater depth.
Example 4×4 shopping plans
4×4 bed filled 8 inches deep
Exact volume: 10.67 cubic feet. With 5% extra: 11.2 cubic feet. Buy 8 bags at 1.5 cubic feet, 6 bags at 2 cubic feet or approximately 0.42 cubic yard including the allowance.
4×4 bed filled 12 inches deep
Exact volume: 16 cubic feet. With 5% extra: 16.8 cubic feet. Buy 12 bags at 1.5 cubic feet, 9 bags at 2 cubic feet or approximately 0.62 cubic yard including the allowance.
Two 4×4 beds filled 12 inches deep
Double the single-bed amount: 32 cubic feet exactly, or 33.6 cubic feet with 5% extra. That equals approximately 1.24 cubic yards including the allowance.
Estimate the soil-mix ingredients
For a 12-inch-deep bed requiring 16 cubic feet, GardenCalcLab's 40/40/20 planning preset becomes:
- 6.4 cubic feet screened topsoil (40%)
- 6.4 cubic feet mature compost (40%)
- 3.2 cubic feet aeration material (20%)
This is a practical starting point rather than a universal recipe. Adjust for the texture of the ingredients, compost quality, climate, crops and the soil beneath the bed.
Bagged soil or bulk delivery?
A single shallow 4×4 bed is often convenient to fill with bags, especially when delivery access is limited. For a 12-inch bed, compare the cost of roughly 0.62 cubic yard including the allowance with the delivered price of bagged soil.
Bulk soil can become more economical when filling several beds, but supplier minimums and delivery fees matter. Add every bed together before asking for a quote.
Common 4×4 calculation mistakes
- Using the frame's outside size: thick lumber can reduce the interior volume.
- Entering inches as feet: divide the depth in inches by 12.
- Filling completely to the rim: leave space for watering and mulch.
- Rounding each ingredient too early: calculate the total volume first.
- Comparing bag weights: use cubic feet or liters to compare volume.
Calculate your exact bed
Change the inside size, soil depth, number of beds or bag volume to get a personalized shopping plan.
Frequently asked questions
How much soil does a 4×4 raised bed need at 12 inches deep?
A 4×4 bed filled 12 inches deep needs 16 cubic feet, or about 0.59 cubic yard. With 5% extra for minor settling and measurement differences, plan for 16.8 cubic feet.
How many bags of soil fill a 4×4 raised bed?
At 12 inches deep with 5% extra, plan for 23 bags at 0.75 cubic foot, 17 one-cubic-foot bags, 12 bags at 1.5 cubic feet, 9 bags at 2 cubic feet or 6 bags at 3 cubic feet.
Is 8 inches deep enough for a 4×4 raised bed?
Eight inches can work for many greens, herbs and compact crops when an open-bottomed bed sits over usable soil. Deep-rooted crops or a hard surface beneath the bed usually require more depth.
Should I add extra soil for settling?
A 5% purchasing allowance is a practical starting point for small measurement differences and minor settling. Loose or highly organic mixes may settle more, so check the supplier's guidance and top up later if needed.