Spike's Calculators

Concrete from Square Footage

Calculate the amount of concrete you will need from an area measured in square feet.
Cubic feet = S * D
where S is the area in square feet
D the depth of the area in inches 
Example Calculation
slab has an area of 425 square feet
the average depth is 4 inches

First convert the 4 inches to feet by dividing by 12.
4 ÷ 12 = 0.3333
4 inches = 0.3333 feet

Calculate the volume in cubic feet by multiplying the area by the dept of the slab.
425 * 0.3333 = 141.6666  rounded to 142
You will need 142 cubic feet of concrete for this slab.


Square Footage of Area ft²
Slab Thickness in.
Waste:   %


Concrete Needed in Cubic Feet: ft³
Cubic Yards: yd³
Cubic Metres:


  1. enter the square footage of the area
  2. the depth of slab in inches
  3. waste factor (if required) in a percentage


  1. amount of concrete needed in cubic feet
  2. in cubic yards
  3. in cubic metres

When Ordering Concrete

This concrete calculator will help you in estimating the amount of concrete needed for your project. The amount given as needed, does not include any waste. It is recommended, depending on the job you are doing, to add anywhere from an extra 4% to 10% to your concrete order to make sure you have enough concrete to finish the job. Ask when ordering the concrete. They will be able to give you a good idea of what is needed.


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