How to Calculate Yards of Concrete

Free calculator for slabs, columns, footings & stairs

Dimensions
Settings
Waste Factor
5%
Price / Yard
$
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Quick Tip: Magic Number 81

For a 4-inch slab, divide square footage by 81 to get cubic yards.

Frequently Asked Questions
How do I calculate yards of concrete for a slab?
Multiply length × width × thickness (in inches), divide by 12 to convert to cubic feet, then divide by 27 to get cubic yards. Example: A 10ft × 12ft × 4in slab = (10 × 12 × 4 ÷ 12) ÷ 27 = 1.48 yards.
How do you calculate yards of concrete for columns?
For round columns: π × (radius in feet)² × height ÷ 27. For square columns: width × depth × height (all in feet) ÷ 27. Our calculator handles both types automatically.
How to calculate concrete yards needed?
Measure your project dimensions in feet, calculate the volume in cubic feet, then divide by 27. Always add 5-10% for waste. Use our calculator above for instant results.
How much does 1 yard of concrete cost?
Ready-mix concrete costs $130-$160 per cubic yard on average, depending on your location and mix strength. Use the price calculator above to estimate your total cost.
How many bags equal 1 cubic yard?
You need approximately 60 bags of 60lb concrete or 45 bags of 80lb concrete to make 1 cubic yard. Our calculator shows both options for your project.