FREE CALCULATOR · ESTIMATE ONLY
Concrete calculator.
Slabs, footings and round columns. Get cubic yards to order, or how many bags to buy.
TL;DR
Enter the size of your slab, footing or column and a waste allowance. The calculator gives cubic feet, cubic yards, cubic yards to order with waste, and how many 40, 60 or 80 lb bags you'd need at typical yields.
5–10% is a common allowance.
Your numbers
Estimate only. Bag counts use typical yields (80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45, 40 lb ≈ 0.30). Check the bag and your supplier, and round up to their order size. Ground prep, forms and over-dig change the real number.
THE MATH
How it works.
- Slab: length × width × (thickness in inches ÷ 12) = cubic feet.
- Footing: length × (width ÷ 12) × (depth ÷ 12) = cubic feet.
- Column: 3.1416 × radius² × height × how many, with the radius in feet.
- Cubic yards = cubic feet ÷ 27. Add your waste percent to get the amount to order.
- Bags = cubic feet with waste ÷ the bag's yield, rounded up.
NEXT STEP
Turn the rough number into a real estimate.
The free Peak estimate tool lays out options, takes the signature and collects the deposit.
QUESTIONS
Common questions.
Multiply length × width × thickness, all in feet, then divide by 27. A 10 × 10 ft slab at 4 inches is about 1.23 cubic yards before waste.
Many crews add 5 to 10 percent for uneven ground and spillage. Ask your supplier what they recommend for the job.
At a typical yield of 0.60 cubic feet per 80 lb bag, about 45 bags make a cubic yard. Check the bag, since yields vary by mix.
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