Concrete Calculator for Slabs and Footings
Enter the length, width and thickness of your slab or footing to see how much concrete you need in cubic feet and cubic yards, plus how many 60 lb and 80 lb bags it takes.
How to estimate concrete
- Enter the slab or footing length and width in feet.
- Enter the thickness in inches (4 inches is common for a slab).
- Set a waste percent to cover spillage and uneven ground.
- Read the cubic yards and bag counts to order your concrete.
Examples
10 by 10 ft slab, 4 inches thick
length 10 ft, width 10 ft, thickness 4 in, 0% waste
33.33 cubic feet, 1.23 cubic yards, 75 sixty-lb bags or 56 eighty-lb bags
Frequently asked questions
How many 60 lb bags are in a cubic yard?
About 60 bags. A 60 lb bag yields roughly 0.45 cubic feet, and a cubic yard is 27 cubic feet, so 27 divided by 0.45 is 60 bags.
When should I order ready-mix instead of bags?
Bags are practical for small jobs. Past roughly 1 cubic yard the bag count climbs fast, so a ready-mix truck is usually cheaper and faster.
How much waste should I add?
Five to ten percent is typical. Uneven subgrade, spillage and over-excavated footings all consume extra concrete, so ordering a little more avoids a short pour.
What thickness should a slab be?
Four inches suits patios and walkways. Driveways and areas that carry vehicles are usually five to six inches thick.
How do I convert cubic feet to cubic yards?
Divide cubic feet by 27, since one cubic yard equals 27 cubic feet. This tool does the conversion for you automatically.
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