Spike's Calculators

Siding - Cladding

Fiber Cement / Engineered Wood Siding Calculator

Calculate the amount of Fibre Cement/Engineered Wood Siding needed to cover a wall.

Siding Exposure Lap

You can use this calculator to calculate the number of boards you need to cover a wall. For this to work, the siding you install has to be in fixed board lengths such as engineered wood and fibre cement siding. If you are using random length boards, use this calculator.

Fibre Cement siding manufactures: James Hardie, GAF, Allura, Nichiha, MaxiTile, Cerber

Engineered Wood Siding Manufactures: LP SmartSide, TFP, Collins, Maibec, Marwood

Siding Calculator

Length of Wall ft inch
Height of Wall ft inch
Wall Openings ft²
Board Length in.
Exposed Face in. n
Waste %


Square Footage of Wall ft²
Amount of Siding
to Cover Wall
# of boards
Waste Factor Adds # of boards
Total Amount of
Siding Needed
# of boards


  1. enter the wall's length in feet and inches
  2. the height of the wall in feet and inches
  3. the combined sections of the wall that don't need siding in square feet
  4. the length of one board in inches
  5. the exposed face (reveal) of one of the boards in inches
  6. an allowance for waste in a percentage


  1. the area of the wall in square feet
  2. the number of boards needed
  3. the number of boards the waste factor adds
  4. the number of boards needed, including waste
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