QuickCheckToolsSiding calculator
Work out the wall area of your house and how many squares and boxes of siding you need, including gables and waste.
How the calculation works
Wall area is the house perimeter times the wall height. Each gable adds a triangle: width × height ÷ 2. We subtract 20 sq ft for each door and 15 sq ft for each window, add your waste allowance, then divide by 100 for squares. Measure the house itself, not the roof overhang.
Questions
How do I calculate how much siding I need?
Multiply the perimeter of the house by the wall height, add the gable triangles (width × height ÷ 2 each), subtract about 20 sq ft per door and 15 sq ft per window, then add 10% for waste. Divide by 100 to get squares.
What is a square of siding?
A square is 100 square feet of wall coverage. Siding is priced and sold by the square, so a 1,375 sq ft job needs 14 squares.
How much extra siding should I buy?
About 10% for a simple rectangular house, and 15% or more if there are lots of corners, dormers or angles, because of cuts and offcuts.
How do I measure a gable?
Measure the width at the base of the triangle and the height from the base to the peak. The area is width × height ÷ 2.
How much siding is in a box?
It varies by brand and profile; many vinyl siding boxes cover about 200 sq ft (two squares). Check the box label and enter its coverage.
Does this include trim and accessories?
No. J-channel, corner posts, starter strip, soffit and fascia are bought separately by length. This calculator covers the main wall siding.
Estimate for the main wall siding on a simple house. Trim, J-channel, corner posts and soffit are extra.