Concrete Slab Calculator
Concrete slab calculator for patios, driveways, sidewalks, and pads.
Estimate how much concrete you need for rectangular slabs, square pads, patios, sidewalks, driveways, garage floors, and shed pads. Use the main concrete calculator to enter dimensions, add waste, switch between imperial and metric units, and estimate material cost.
How to calculate concrete for a slab
For a rectangular concrete slab, multiply length by width by thickness. If you are using imperial measurements, enter length and width in feet and thickness in inches. The calculator converts the result into cubic feet and cubic yards.
Formula
Length × Width × Thickness = Concrete Volume
Most concrete slab estimates should include extra material for waste, uneven base conditions, forms, spillage, and small measurement differences. A common waste allowance is 5% to 10%.
Concrete slab example
A 10 ft by 10 ft slab that is 4 inches thick has a volume of about 33.33 cubic feet. Since one cubic yard equals 27 cubic feet, that is about 1.23 cubic yards before waste. With 10% waste, the estimate is about 1.36 cubic yards, usually rounded up to a practical order amount.
Slab calculator FAQ
How thick should a concrete slab be?
Many patios, sidewalks, and shed pads use 4 inches as a common slab thickness, but requirements can vary by project, soil, load, reinforcement, and local code.
Should I add waste to a slab estimate?
Yes. A 5% to 10% waste allowance is commonly used for planning because real pours can require extra concrete.
Can I calculate concrete slabs in metric units?
Yes. The Numeravo concrete calculator supports metric inputs using meters and centimeters and outputs cubic meters.
Does the slab calculator include labor?
No. The calculator estimates concrete volume and material cost only. Labor, delivery, forms, reinforcement, gravel, and finishing costs are separate.