Square feet to cubic yards
Multiply the square feet by the depth in inches and divide by 324. 500 sq ft at 3 in deep is 4.63 cubic yards.
Why you need a depth
Square feet measure area and cubic yards measure volume, so there is no direct conversion between them; you need a depth to turn an area into a volume. Extension services use the shortcut square feet × depth in inches ÷ 324, because a cubic yard spread 1 in thick covers 324 sq ft (27 cu ft is 324 slices one inch thick).
500 sq ft × 3 in = 125 cu ft ÷ 27 = 4.63 cu yd
If the depth is in feet, multiply square feet by the depth in feet and divide by 27 instead.
Cubic yards for common areas
| Area | 1 in | 2 in | 3 in | 4 in | 6 in |
|---|---|---|---|---|---|
| 50 sq ft | 0.15 | 0.31 | 0.46 | 0.62 | 0.93 |
| 100 sq ft | 0.31 | 0.62 | 0.93 | 1.23 | 1.85 |
| 150 sq ft | 0.46 | 0.93 | 1.39 | 1.85 | 2.78 |
| 200 sq ft | 0.62 | 1.23 | 1.85 | 2.47 | 3.70 |
| 250 sq ft | 0.77 | 1.54 | 2.31 | 3.09 | 4.63 |
| 300 sq ft | 0.93 | 1.85 | 2.78 | 3.70 | 5.56 |
| 400 sq ft | 1.23 | 2.47 | 3.70 | 4.94 | 7.41 |
| 500 sq ft | 1.54 | 3.09 | 4.63 | 6.17 | 9.26 |
| 750 sq ft | 2.31 | 4.63 | 6.94 | 9.26 | 13.89 |
| 1,000 sq ft | 3.09 | 6.17 | 9.26 | 12.35 | 18.52 |
| 1,500 sq ft | 4.63 | 9.26 | 13.89 | 18.52 | 27.78 |
| 2,000 sq ft | 6.17 | 12.35 | 18.52 | 24.69 | 37.04 |
These are exact volumes. Mulch, topsoil and gravel are usually ordered in whole or half yards, so round up; loose soil and mulch also settle after spreading.
Sources
- How Much Compost, Soil or Mulch Do I Need to Purchase?, Texas AgriLife Extension Service, Travis County, February 2010. Square feet times depth in inches, divided by 324, gives cubic yards.