Siding Calculator

Siding or cladding for walls and gable ends, less doors and windows: squares, boxes, linear feet and the number of boards or panels at your exposure.

Siding is estimated in squares, where one square is 100 ft² of wall. Add up each wall (length × height) and each gable end (half the width × the height), take off doors and windows, and add about 10% for cuts. A 40 × 9 ft wall and a 24 ft wide gable 8 ft high come to 456 ft²; less a door and two windows, plus 10%, that's 4.53 squares. At an 8 inch exposure that's about 680 linear feet of siding, or 55 panels 12 ft 6 in long. The same sum works for cladding and weatherboards in metres: enter the cover width and board length and the calculator gives the linear metres and boards.

Units
Measure by
Walls
ft
ft
ft
ft
Feet and inches work too: type 12'6 or 12.5.
Doors and windows to leave out
ft
ft
ft
ft
%
in
ft
Squares
4.53

1 square = 100 ft², incl. extra

Boards or panels
55

12.5 ft long

Linear length
679.8 ft

of boards at that exposure

Boxes
3

at 2 squares per box

How it was worked out
  1. Wall 1: 40 ft × 9 ft = 360 ft²
  2. Wall 2: triangle: ½ × 24 ft × 8 ft = 96 ft²
  3. Less 1 door (20 ft²) and 2 windows (24 ft²) = −44 ft²
  4. Area to cover: 412 ft²
  5. Plus 10% for cuts and waste = 453.2 ft²
  6. 453.2 ft² ÷ 100 = 4.53 squares
  7. 453.2 ft² ÷ 8 in exposure = 679.8 ft of boards ÷ 12.5 ft each = 55 boards

Exposure is the part of each board that shows once it's lapped or fitted. Trims, corners, starter strips and soffits are separate; measure their lengths around the openings and corners.

Common use cases

  • Estimate vinyl, fibre cement or wood siding for a house or garage
  • Count weatherboards or cladding boards for an extension or shed
  • Work out the gable ends as well as the walls
  • Compare panel lengths and exposures

How to use

  1. Enter each wall's width and height; switch a row to Triangle for a gable end.
  2. Enter the doors and windows to leave out.
  3. Enter the exposure (the part of each board that shows) and the board or panel length.
  4. Read the squares or area, boards and boxes.

FAQ

What is a square of siding?

100 ft² of wall. Siding is priced and packaged by the square; many vinyl siding brands pack about two squares per box, but check the carton.

How do I measure a gable end?

Measure its width at the bottom and its height from the bottom of the triangle to the peak, then multiply them and halve the result. Switch a row to Triangle and the calculator does this.

What exposure should I use?

The exposure is how much of each board shows once it's installed. Double 4 vinyl siding has an 8 in exposure and double 5 has 10 in; lap siding and weatherboards vary, so use the figure from the product.

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