Enter your slab, column, or cylinder dimensions — Length, Width, Thickness, Diameter, or Depth depending on Calculation Type — along with Concrete Density and Waste Factor, and the Concrete Weight Calculator gives you the Total Weight, Volume, and how many bags you need.
Total Weight
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Volume
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60-lb Bags Needed
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80-lb Bags Needed
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Standard concrete typically weighs 150 pounds per cubic foot. Lightweight concrete weighs around 145 lbs/ft³, while heavy-weight concrete can weigh up to 160 lbs/ft³.
Multiply length × width × thickness. Convert thickness from inches to feet by dividing by 12. For example, a 10×10 ft slab that's 4 inches thick = 10 × 10 × (4/12) = 33.33 cubic feet.
Adding 5-15% waste factor accounts for spillage, over-excavation, and irregularities in the subgrade. This ensures you have enough concrete to complete your project.
A 60-lb bag yields about 0.45 cubic feet, while an 80-lb bag yields about 0.6 cubic feet. Divide your total volume by the yield per bag to determine how many bags you need.
There are 27 cubic feet in 1 cubic yard. Concrete is often sold by the cubic yard for large projects, while bags are measured in cubic feet coverage.
Use the formula π × radius² × depth. For a 3-foot diameter footing that's 2 feet deep: 3.14159 × (1.5)² × 2 = 14.14 cubic feet.
Yes, it's recommended to order 5-10% more than calculated to account for waste, spillage, and minor measurement variations. Running short during a pour can be costly and affect quality.