Concrete Slab Calculator
Calculate how much concrete you need for a slab — in cubic yards and bags of concrete.
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Concrete Needed
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Volume
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80 lb Bags
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60 lb Bags
Recent Calculations
What Is Concrete Slab?
Concrete for a slab is measured in cubic yards. Knowing the exact amount prevents expensive waste or mid-project shortages.
Formula
Volume = Length × Width × (Thickness/12), then divide by 27 for cubic yardsExample
A 20' × 10' slab, 4" thick needs 20×10×0.333 = 66.7 cu ft = 2.47 cubic yards.
Frequently Asked Questions
How much extra concrete should I order?
Order 5-10% extra to account for spillage, uneven ground, and form rounding.
What thickness for a driveway?
Standard residential driveway is 4" thick. Heavy vehicles need 5-6". Sidewalks are typically 4".