Concrete Calculator
Calculate concrete volume, bags needed, and estimated cost for your project.
How Concrete Calculation Works
Concrete is sold by the cubic yard (or cubic meter). To determine how much you need, calculate the volume of the area you want to fill. For a slab, multiply length by width by thickness. For a column, use the cylinder formula: pi times radius squared times height.
Walls are calculated similarly to slabs: length times height times thickness. For staircases, each step is treated as a rectangular block, and the volumes are summed. Always add a 10% waste factor to account for spillage, uneven surfaces, and over-excavation.
Pre-mixed concrete bags come in 40 lb, 60 lb, and 80 lb sizes. Each covers a different volume: 40 lb covers about 0.011 cubic yards, 60 lb about 0.017 cubic yards, and 80 lb about 0.022 cubic yards. For larger projects, ordering ready-mix by the cubic yard is more economical. Need help with the math? Use our Online Calculator for quick arithmetic or the Fraction Calculator for working with mixed measurements.