Concrete Calculator
Estimate concrete for slabs, footings, walls, and columns with waste and bag counts
Imperial mode uses feet for length, width, and height. Use inches for thickness, depth, and diameter.
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Bag note: Bag yields vary by mix and manufacturer. Use the bag estimate as a planning guide and confirm the yield printed on your product.
Concrete Needed
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Calculation Steps
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How Concrete Volume Is Estimated
Each shape uses a simple volume formula, then applies your waste allowance.
Shape formulas
Slabs and footings use rectangular volume formulas. Walls use length by height by thickness. Columns use pi times radius squared times height.
Waste allowance
Concrete projects commonly include extra material for uneven subgrade, form variation, spillage, and finishing. Adjust the waste percentage to match the job.
Bags vs ready-mix
Small jobs can be planned by bag count. Larger pours are usually ordered in cubic yards or cubic meters from a ready-mix supplier.
Concrete Examples
Quick reference estimates for common small concrete projects.
Patio slab
10 ft x 12 ft x 4 in with 10% waste = 1.63 yd
Metric pad
3 m x 2 m x 10 cm with 5% waste = 0.63 m
Round column
12 in diameter x 8 ft = 0.23 yd before waste