Concrete Calculator
Concrete & Masonry · Updated July 2026
Enter the length, width, and thickness of your slab, footing, or pad to find exactly how much concrete you need — in cubic yards and in 60 lb and 80 lb bags.
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Estimates only. Add extra for waste and confirm with your supplier.
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How much concrete do I need?
Multiply length × width × thickness (in feet) to get cubic feet, then divide by 27 for cubic yards. A 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards.
How to measure for a concrete pour
Measure the length and width of the form in feet and the thickness in inches. For footings, price each run separately; for slabs, break L-shapes into rectangles and add them. Order 5–10% extra — spillage, uneven subgrade, and over-excavation all eat into a pour, and running short mid-slab means a cold joint.
Bags vs. ready-mix
Bagged concrete is convenient for small jobs: an 80 lb bag yields about 0.6 cu ft, so it takes roughly 45 bags per cubic yard. Once you pass about 1 cubic yard (roughly 50+ bags), ready-mix delivery is usually cheaper and far less work than mixing by hand.
How to use this calculator
- 1Measure length and width in feet.
- 2Measure the thickness (depth) in inches.
- 3The calculator converts to cubic yards and bag counts automatically.
Frequently asked questions
How many 80 lb bags of concrete in a cubic yard?
An 80 lb bag yields about 0.6 cubic feet, so it takes roughly 45 bags to make one cubic yard of concrete.
How many bags of concrete are in a yard?
About 45 bags of 80 lb concrete, or 60 bags of 60 lb, make up one cubic yard.
How thick should a concrete slab be?
4 inches is standard for patios and walkways; use 5–6 inches for driveways or anywhere vehicles park.
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