Area times depth, divided by 324
Material is sold by volume but you measure a patch by area, so the two have to meet. The long way is area × depth-in-feet, then ÷ 27 (since 1 yd³ = 27 ft³). The shortcut folds the inch-to-foot step in: 12 × 27 = 324, so you can work straight from inches. Keep depth in inches and the same divisor always works.
What one cubic yard covers, by depth
| Depth | Coverage per yd³ | Typical use |
|---|---|---|
| 1" | 324 ft² | Thin top-dress |
| 2" | 162 ft² | Mulch refresh |
| 3" | 108 ft² | Mulch, gravel base |
| 4" | 81 ft² | Concrete slab, new lawn soil |
| 6" | 54 ft² | Heavy-duty slab, deep beds |
| 12" | 27 ft² | Raised beds, deep fill |
Coverage and depth are inversely proportional: halve the depth and one yard covers twice the area.
Getting the order right
- Cubic feet is not cubic yards. They differ by 27×. Forgetting the ÷ 27 (or ÷ 324) is the classic order that comes in far too large.
- Measure average depth. Ground is rarely flat. For an uneven area, split it into rectangles, work each out, and add them together.
- Add a buffer. Gravel and soil settle when compacted, and some spills as you spread. Order 5 to 15 percent over and round up to the next full yard.
- Weight varies by material. A cubic yard is about 2,700 lb of gravel, 2,200 lb of topsoil, 400 to 800 lb of mulch, and roughly 4,050 lb of concrete — worth knowing for delivery limits.
Common questions
How do I convert square feet to cubic yards?
Multiply the area in square feet by the depth in inches, then divide by 324. For 200 square feet at 4 inches deep: 200 x 4 = 800, divided by 324 is about 2.5 cubic yards.
How much does one cubic yard of material cover?
At a 3-inch depth one cubic yard covers 108 square feet; at 4 inches it covers 81 square feet. Shallower spreads go further, so 2 inches of mulch covers 162 square feet.
Why order more than the calculator says?
Uneven ground, spillage while spreading, and settling of gravel or soil all eat into coverage. Adding 5 to 15 percent and rounding up to a full yard avoids a second delivery.
