Concrete calculator
Choose slab or column, enter the size, and get the volume and bag count.
What you enter stays on this page and is not sent anywhere.
Enter the size to see how much concrete you need.
Source, checked October 19, 2026: QUIKRETE Concrete Mix 1101 data sheet
How to use it
- Pick the measuring system and the shape: slab or footing, or round column.
- Enter the size and an extra allowance for waste.
- Pick your bag size. Read the volume and the number of bags to buy.
Questions
How is the concrete volume calculated?
A slab or footing is length times width times thickness. A round column is pi times radius squared times height. The extra allowance is then added on top.
Where do the bag yields come from?
From the QUIKRETE Concrete Mix data sheet: an 80 lb bag yields about 0.60 cubic feet, a 60 lb bag 0.45 and a 40 lb bag 0.30. Other brands and sizes differ, so use Custom with the yield on your bag.
How much extra should I add?
Spills, uneven ground and over-digging use up concrete, so people add a margin. The box starts at 5 percent. Raise it for rough ground and round bags up.
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