Yardwise

Siding calculator

How much siding a house needs, including the triangle gable ends, in squares and boxes.

Measurements in feet and inches. Updated .

Siding to buy
Boxes
Walls
Gables

Doors are counted as 21 sq ft and windows as 15 sq ft. A square is 100 sq ft.

How to use it

Enter the house's length, width and wall height to the eaves in feet. For each gable end (the triangle of wall under a pitched roof), enter its width and its height from the eaves to the peak. Then count the doors and windows. The calculator works out the area to cover and how many squares and boxes of siding to buy.

Siding is sold by the square, which covers 100 sq ft. Vinyl siding often comes 2 squares to a box; check the label of the product you're buying and change Squares per box to match.

How it's calculated

  1. Wall area = 2 × (length + width) × wall height.
  2. Gable area = number of gables × (gable width × gable height ÷ 2).
  3. Subtract 21 sq ft per door and 15 sq ft per window.
  4. Add the waste allowance, then squares = area ÷ 100, rounded up.
  5. Boxes = squares ÷ squares per box, rounded up.

With the default 40 × 28 ft house, 9 ft walls and two 28 ft gables 7 ft tall: 1,224 sq ft of wall plus 196 sq ft of gables, minus 192 sq ft of openings, is 1,228 sq ft. With 10% extra that's 14 squares, or 7 boxes.

Tips

  • Measure each wall separately if the house isn't a simple rectangle, and add the areas. Garages and bump-outs add up quickly.
  • Trim is separate. Corner posts, J-channel, starter strip, soffit and fascia are sold by the piece or linear foot, not by the square.
  • Use 15% extra for houses with many corners, dormers or angled walls, where more pieces get cut.
  • Large windows and garage doors: measure them and subtract their actual area instead of the 15 sq ft window allowance.