Concrete Slab Calculator
Calculate cubic yards for a slab or driveway, 80-lb bags for small pours, and a rough material cost. Free concrete calculator for contractors and DIYers.
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See it on Etsy →Cubic yards formula
Length × width × (thickness in inches ÷ 12) ÷ 27 = cubic yards. Add 5–10% for over-excavation and spillage. An 80-lb bag yields about 0.6 cubic feet.
For contractors: price the whole job
Concrete is only part of the cost. Demo, base, reinforcement, forms, finishing labor, pump, short-load fees and haul-off all need to be priced to your margin.
FAQ
How many yards for a 24x24 slab at 4 inches?
About 7.1 cubic yards, so order 7.5–8.
How many 80-lb bags make a yard?
About 45 bags per cubic yard.