The formula
cubic yards = square feet × depth (in) ÷ 324
Where 324 comes from: depth in inches ÷ 12 gives feet, and cubic feet ÷ 27 gives cubic yards. 12 × 27 = 324, so you can do both steps at once.
If your depth is already in feet, use square feet × depth (ft) ÷ 27.
Example: a 25 × 20 ft area is 500 square feet. At 4 inches deep: 500 × 4 ÷ 324 = 6.17 cubic yards.
Square feet to cubic yards table
| Area | 2 in deep | 3 in deep | 4 in deep | 6 in deep |
|---|---|---|---|---|
| 50 sq ft | 0.31 | 0.46 | 0.62 | 0.93 |
| 100 sq ft | 0.62 | 0.93 | 1.23 | 1.85 |
| 200 sq ft | 1.23 | 1.85 | 2.47 | 3.70 |
| 250 sq ft | 1.54 | 2.31 | 3.09 | 4.63 |
| 400 sq ft | 2.47 | 3.70 | 4.94 | 7.41 |
| 500 sq ft | 3.09 | 4.63 | 6.17 | 9.26 |
| 750 sq ft | 4.63 | 6.94 | 9.26 | 13.89 |
| 1,000 sq ft | 6.17 | 9.26 | 12.35 | 18.52 |
All figures in cubic yards, before any allowance for waste.
Cubic yards to square feet
Going the other way tells you how far a delivery will spread:
square feet covered = cubic yards × 324 ÷ depth (in)
| Cubic yards | At 2 in | At 3 in | At 4 in | At 6 in |
|---|---|---|---|---|
| 1 | 162 sq ft | 108 sq ft | 81 sq ft | 54 sq ft |
| 2 | 324 | 216 | 162 | 108 |
| 3 | 486 | 324 | 243 | 162 |
| 5 | 810 | 540 | 405 | 270 |
| 10 | 1,620 | 1,080 | 810 | 540 |
Square yards
Some plans and flooring or paving quotes use square yards. One square yard is 3 ft × 3 ft = 9 square feet.
- Square feet to square yards: ÷ 9 (450 sq ft = 50 sq yd)
- Square yards to square feet: × 9
- Square yards to cubic yards: square yards × depth in inches ÷ 36
The 36 works because a square yard is already 9 square feet, and 324 ÷ 9 = 36. The converter at the top accepts square yards and square meters too.
For concrete
The same formula gives yards of concrete for a slab. A 24 × 24 ft garage floor at 4 inches is 576 × 4 ÷ 324 = 7.11 cubic yards. Concrete is ordered with a little extra for uneven subgrade and spillage, often 5 to 10 percent. The concrete slab calculator adds that allowance and the bag counts, and how to calculate yards of concrete covers footings and steps.
Measuring the area well
- Rectangles: measure both sides at the edges, not across the middle of a sagging tape.
- Odd shapes: split them into rectangles, triangles and circles and add the areas. The cubic yard calculator takes one section per shape.
- Depth: take several readings and average them. A single shallow spot can make a big difference over a large area: 1,000 sq ft at 3 in is 9.26 cubic yards, at 4 in it is 12.35.
These conversions give the geometric volume. Loose materials can settle once spread, and a supplier's yard is measured loose, so ask whether they suggest ordering extra for your material.
Questions people ask
- How do I convert square feet to cubic yards?
- Multiply square feet by the depth in inches and divide by 324. For 500 sq ft at 4 inches: 500 × 4 ÷ 324 = 6.17 cubic yards.
- How many square feet does 1 cubic yard cover?
- 324 ÷ depth in inches. That is 162 sq ft at 2 inches, 108 at 3 inches, 81 at 4 inches and 54 at 6 inches.
- How many square feet are in a square yard?
- 9. A square yard is 3 ft × 3 ft. Divide square feet by 9 to get square yards.
- How do I convert square yards to cubic yards?
- Multiply square yards by the depth in inches and divide by 36. 50 square yards at 4 inches is 50 × 4 ÷ 36 = 5.56 cubic yards.
- How many yards of concrete do I need for 1,000 square feet?
- At 4 inches thick, 1,000 × 4 ÷ 324 = 12.35 cubic yards. At 6 inches, 18.52 cubic yards. Add 5 to 10 percent before ordering.