Concrete Calculator
Cubic yards, bags and cost for a slab or patio. Change the numbers and the result updates instantly.
How it works
Concrete is sold by the cubic yard. Multiply length by width (in feet) by thickness (in feet) to get cubic feet, then divide by 27. Order about 10% extra for uneven ground and spillage. An 80-pound bag of mix makes about 0.6 cubic feet, a 60-pound bag about 0.45.
Example
Example: a 12 ft by 10 ft patio 4 inches thick needs about 1.5 cubic yards, or 2 yards with 10% extra. That is about 74 bags of 80-pound mix including the extra.
Tips
- Change one input at a time to see what moves the result most.
- Use realistic rates. Check current averages before you decide.
- Results are estimates and do not replace advice from a licensed professional.
Frequently asked questions
Is this calculator free?
Yes. There is no sign-up and nothing is stored on our servers; the math runs in your browser.
How accurate is it?
It uses standard formulas, but real offers include fees, rate changes and taxes that can differ. Treat the result as an estimate.
Sources and method
Page last updated November 2026. See our editorial policy and disclaimer.