Siding Calculator
Enter your home's total exterior wall area to calculate how many squares of siding to order — siding is conventionally sold and estimated in 'squares,' where one square covers 100 square feet.
How the Siding formula works
A coverage-based calculation using the standard siding 'square' unit:
Squares needed = ceil( Wall area (ft²) / 100 × (1 + Waste%) )
Step-by-step calculation
- Calculate total exterior wall area to be sided, subtracting large openings like windows and doors if desired.
- Divide by 100 (one 'square' of siding covers 100 ft²).
- Increase by a waste percentage for cuts and corners, then round up to a whole square.
Worked example
A home with 1,800 ft² of exterior wall area, with 12% waste: Squares = ceil(1,800/100 × 1.12) = ceil(20.16) = 21 squares.
Frequently asked questions
Why is siding measured in 'squares' instead of square feet directly?
It's a longstanding construction industry convention — one square (100 ft²) is a convenient unit for estimating and ordering materials like siding and roofing, making quantities easier to work with than raw square footage.
Should I subtract window and door area from the total?
Many contractors do subtract large openings for a more precise material estimate, though some prefer to leave a buffer by not subtracting smaller openings, since waste from cutting around them is often comparable to the area saved.