Spike's Calculators

Concrete Slab Calculator - Imperial

Concrete Calculator For Slabs

Calculate the amount of concrete needed for a slab using feet and inches for measurements. This calculator provides results in cubic feet, cubic yards and cubic metres.

Concrete Slab

Length ft in
Width ft in
Depth in
Square Footage of Slab ft²
Amount of Concrete Needed in:
Cubic Feet ft³
Cubic Yards yd³
Cubic Metres


  1. enter the length of the slab in feet and inches
  2. the width of the slab in feet and inches
  3. thickness of the slab inches


  1. square footage of the slab
  2. amount of concrete needed in cubic feet
  3. concrete needed in cubic yards
  4. concrete needed in cubic metres

one cubic inch (in³) = 0.000578703703703704 cubic feet (ft³)
one cubic inch (in³) = 0.0000214334705075445 cubic yards (yd³)
one cubic inch (in³) = 0.000016387064 cubic metres (m³)

To convert cubic feet to cubic yards, multiply cubic feet * 0.037037037037037
To convert cubic feet to cubic metres, multiply cubic feet * 0.028316846592
To convert cubic yards to cubic metres, multiply cubic yards * 0.764554857984

Formula's used:

length * width * depth = V

Example calculation:
slab length = 25'
width = 12'-8"
concrete slab thickness = 6"
It all has to be in the same units. It would be possible to change it all into inches, but that makes for large numbers so it will be easier to convert the inches into a foot value.

12'-8" convert 8 inches into feet by dividing by 12
8 ÷ 12 = 0.666 feet
12'-8" then becomes 12.666 feet

Next convert the 6" into a foot value by dividing this amount by 12
6 ÷ 12 = 0.5 feet
Now you can fractions the concrete volume for this slab by multiplying the length, width and depth values together.
25 * 12.666 * 0.5 = 158.325 cubic feet
You will need 158.3 cubic feet of concrete for this slab

Usually, the cost for the concrete is for a price per cubic yards or cubic metres.

To change cubic feet to cubic yards: There are 27 cubic feet in one cubic yard. Divide your cubic feet amount by 27 to get to the cubic yard volume of concrete.
158.325 ÷ 27 = 5.86 cubic yards.

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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