Enter your Slab Length, Slab Width, and Slab Thickness, along with the Number of Slabs, any Hole dimensions to subtract, and a Waste Factor — the Concrete Slab Calculator gives you the total Concrete Volume Needed in cubic feet, plus Estimated Weight and exactly how many 60lb or 80lb bags to grab from the store.
Concrete Volume Needed
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Volume in Cubic Feet
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Estimated Weight
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60lb Bags Needed
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80lb Bags Needed
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To calculate concrete for a slab, multiply length × width × thickness. Convert thickness from inches to feet by dividing by 12, then divide the result by 27 to get cubic yards. Always add 5-15% extra for waste.
An 80lb bag of concrete covers approximately 0.6 cubic feet or 0.022 cubic yards. Divide your total cubic yards by 0.022 to determine the number of 80lb bags needed.
Standard concrete slab thickness varies by use: 4 inches for sidewalks and patios, 4-6 inches for driveways and garage floors, and 6+ inches for heavy-duty applications or areas with heavy vehicle traffic.
Standard concrete weighs approximately 4,000-4,050 pounds per cubic yard. This can vary slightly depending on the mix design and aggregate type used in the concrete.
Yes, always order 5-15% extra concrete to account for waste, spillage, and minor measurement variations. It's better to have slightly too much than to run short during the pour.
Yes, this calculator works for any rectangular concrete structure. For footings, enter the footing dimensions. For walls, use length × height × thickness to calculate volume.
Enter the diameter and depth of any holes or cutouts in the holes section. The calculator will subtract this volume from your total concrete needs automatically.
Cubic yards are the standard unit for ordering concrete. One cubic yard equals 27 cubic feet. Most concrete suppliers price and deliver concrete by the cubic yard.