Concrete yardage calculator
Concrete is sold by the cubic yard, but you measure in feet and inches. This calculator does the conversion, shows the exact yardage, and tells you how many yards to order once waste and quarter-yard rounding are included.
Calculator
Your estimate
Enter your measurements and select Calculate to see how much to order.
- Concrete to order
- cu yd
- Exact volume
- cu yd / cu ft
- Bags of 80 lb mix
- Cost with bags
- Cost with ready-mix
- Best way to buy
How it is calculated: length × width × thickness in feet gives cubic feet. Divide by 27 for cubic yards, then add your extra for waste and round up to the next quarter yard.
How to convert measurements to cubic yards
A cubic yard is a cube 3 ft on each side, so it holds 3 × 3 × 3 = 27 cubic feet. To get yardage, find the volume in cubic feet and divide by 27. The only catch is that thickness is usually measured in inches, and it must be in feet before you multiply.
Cubic yards = length (ft) × width (ft) × thickness (in) ÷ 12 ÷ 27
A shortcut that skips a step: divide by 324 instead of dividing by 12 and then by 27, because 12 × 27 = 324.
Cubic yards = length (ft) × width (ft) × thickness (in) ÷ 324
Worked example
A 30 × 15 ft pad at 5 in thick:
- 30 × 15 × 5 = 2,250
- 2,250 ÷ 324 = 6.94 cu yd exact
- With 10% waste: 7.64 cu yd, so order 7.75 cu yd
Yardage for common slab sizes at 4 in
| Slab | Square feet | Cubic yards | Order with 10% |
|---|---|---|---|
| 8 × 10 ft | 80 | 0.99 | 1.25 |
| 10 × 10 ft | 100 | 1.23 | 1.50 |
| 10 × 12 ft | 120 | 1.48 | 1.75 |
| 12 × 12 ft | 144 | 1.78 | 2.00 |
| 12 × 16 ft | 192 | 2.37 | 2.75 |
| 16 × 20 ft | 320 | 3.95 | 4.50 |
| 20 × 20 ft | 400 | 4.94 | 5.50 |
| 24 × 24 ft | 576 | 7.11 | 8.00 |
One square foot at 4 in is 0.01235 cu yd, so you can also multiply square feet by 0.01235.
Other useful conversions
- 1 cubic yard = 27 cubic feet = 0.765 cubic metres = 45 bags of 80 lb mix
- 1 cubic foot = 0.037 cubic yards = 7.48 US gallons
- 1 cubic metre = 1.308 cubic yards = 35.31 cubic feet
- 1 cubic yard of concrete weighs roughly 2 tons when placed; ask your plant for the mix’s unit weight if it matters for your truck or trailer.
Why the ordering figure is different from the exact figure
The exact yardage is what the shape holds. The ordering figure adds the waste allowance for uneven ground and spills, then rounds up to the next quarter yard because that is the increment plants deliver in. Both are shown so you can see how much is math and how much is margin.
Frequently asked questions
How many square feet does a yard of concrete cover?
At 4 in thick, one cubic yard covers 81 square feet. At 6 in it covers 54 square feet, and at 3 in it covers 108 square feet. Divide 324 by the thickness in inches to get square feet per yard.
How many yards is a 20 by 20 slab?
At 4 in thick, 20 × 20 × 4 ÷ 324 = 4.94 cubic yards. With 10% waste that is 5.43, so order 5.5 cubic yards.
Is a yard of concrete the same as a cubic yard?
Yes. When concrete suppliers say a yard they mean a cubic yard, 27 cubic feet. The same is true of gravel and topsoil suppliers.