Concrete Calculator
Estimate a rectangular concrete pour in cubic yards and in bags of mix.
Use it before you order a pour, when you have length, width, and thickness.
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How we calculated this
Volume is length times width times thickness. Thickness is converted from inches to feet. Waste is added before converting to cubic yards (divide cubic feet by 27). Bag counts round up.
What does this mean?
Order about 1.87 cubic yards, or 85 bags of 80 lb mix, including the waste allowance.
Your assumptions
Edit assumptions- Length
- 12.0 ft
- Width
- 12.0 ft
- Thickness
- 4.00 in
- Waste
- 5%
This calculator provides an estimate for planning. Material yield, waste, prices, and local requirements may vary.
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How the estimate is calculated
Volume is length times width times thickness, with thickness converted from inches to feet.
Waste is added, then cubic feet are divided by 27 for yards. Bag counts use 0.60 cubic feet for an 80 lb bag and 0.45 for a 60 lb bag, rounded up.
Concrete volume
Cubic yards equal length × width × thickness in feet × (1 + waste), divided by 27.
Example
- Measure the inside of the forms in feet.
- Enter thickness in inches. Four inches is a common starting point for a walk or patio.
- Add waste if the base is uneven.
With the numbers filled in on this page, the estimate is 1.87 cubic yards.
What changes the result
Thickness
A small change in inches changes the order. Driveways are often thicker than a 4-inch patio.
Bag yield
Yields vary by brand. The 0.60 and 0.45 cubic foot figures are planning yields.
Ready-mix minimums
A truck may have a minimum order that is larger than a small pad.
Questions
How many cubic feet are in a yard?
Twenty-seven.
Should I order extra?
The waste field is there for that. Many pours add 5% to 10%.
Is this a slab or a pad?
This is the general pour. The slab and pad calculators start with defaults for those jobs, and the pad adds a gravel base.