Spike's Calculators

Octagon Shaped Slab Concrete Calculator

Calculator for Octagon shapes

Calculate the amount of concrete you need for a slab in the shape of an octagon.

In a regular Octagon, there are eight straight, equal-length sides and eight inside corners that total 135°. To calculate the volume of an Octagon shaped slab, you need to provide the length of one side in feet and the required depth of the slab in inches.

Octagon Shaped Volume Calculator - Imperial

Side Length:   ft  in
Depth:   in
Area:   ft ²
Perimeter:   lin ft

Amount of concrete needed:

Cubic Feet:   ft ³
Cubic Yards:   yd ³
Cubic Metres:   m ³


  1. enter the length of a side in feet and inches
  2. the slab thickness (depth) in inches


  1. the area of the slab in square feet
  2. the perimeter of the slab in lineal feet for forming material
  3. the amount of concrete needed in cubic feet
  4. in cubic yards
  5. 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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