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Concrete Calculator
This concrete calculator estimates the volume of concrete needed for a slab. Enter length, width, and thickness to get cubic feet and cubic yards, with optional waste allowance.
Quick answer
Volume is based on slab length x width x thickness.
What this tells you
- •Volume is based on slab length x width x thickness.
- •Thickness is converted from inches to feet for volume calculations.
- •Waste percentage increases recommended order quantity.
How to Use
- 1Enter slab length in feet.
- 2Enter slab width in feet.
- 3Enter slab thickness in inches.
- 4Add optional waste percentage.
- 5Calculate to get cubic feet and cubic yards required.
How It Works
Formula
Cubic Feet = Length(ft) x Width(ft) x Thickness(ft)
Cubic Yards = Cubic Feet / 27
Total with Waste = Cubic Yards x (1 + Waste%)Concrete is typically ordered in cubic yards, so the calculator converts slab volume from cubic feet to cubic yards.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Patio slab estimate
Length20 ft
Width10 ft
Thickness4 in
Waste10%
Result2.72 cubic yards recommended
Common mistakes
- Entering thickness in feet instead of inches
- Ignoring waste allowance for overage and spillage
- Forgetting to convert cubic feet to cubic yards when ordering
Frequently Asked Questions
There are 27 cubic feet in 1 cubic yard.
Yes. A 5-10% waste allowance is commonly used.
This version is optimized for rectangular slabs.