Siding Calculator
Enter your total wall area and a waste allowance to find how many siding squares you need.
Siding is commonly sold by the "square," where 1 square = 100 square feet of coverage.
How siding squares are calculated
This calculator adds your waste allowance to the total wall area, then divides by 100 since siding is traditionally sold in "squares" — a roofing and siding industry unit equal to 100 square feet of coverage — and rounds up since you can't buy a partial square.
A 10% waste allowance covers typical cuts around windows, doors, and corners for a straightforward installation. More complex wall shapes, dormers, or intricate trim work often need a higher allowance.
Frequently asked questions
Why is siding measured in "squares" instead of square feet?
The "square" is a traditional unit in roofing and siding trades, simplifying pricing and ordering — 1 square always equals 100 square feet, making it easy to estimate materials and costs without working with large square-foot numbers.
Should I subtract window and door area from my wall area first?
For a rough estimate, many contractors skip subtracting small openings since the waste allowance covers the cuts. For large openings (garage doors, picture windows), subtracting their area first gives a more accurate material estimate.
How much waste allowance should I use?
10% is typical for a straightforward rectangular home. Homes with many corners, dormers, or architectural details often need 15-20% to account for the additional cuts and fitting required.