Siding Calculator
Calculate the squares of siding you need for your home's exterior, minus doors and windows, with a waste allowance built in.
Squares needed
11.85sq
With waste
1185ft²
Net wall area
1077ft²
1 square of siding = 100 sq ft of coverage, the standard unit siding is sold in. Gable ends and dormers aren't included — add their triangular area to length × width manually if your home has them.
How the siding calculator works
Siding coverage starts with your home's wall area — perimeter times height — minus the openings that won't be sided over, then inflated by a waste percentage for cuts and overlaps, and finally converted into squares (the unit siding is sold in).
Formula: perimeter = 2 × (length + width). Gross area = perimeter × wall height. Net area = gross − (doors × 21) − (windows × 15). Total with waste = net × (1 + waste% ÷ 100). Squares = total ÷ 100.
Frequently asked questions
A square is the standard unit siding is bought and sold in — 100 square feet of finished wall coverage, regardless of the panel or plank size. Dividing your total area by 100 tells you how many squares to order.
10% is standard for horizontal lap siding. Vertical or board-and-batten styles run closer to 12%, and shake or shingle siding needs about 15% due to the extra cutting. Homes with lots of corners or architectural detail can need up to 20%.
No — this calculator covers the rectangular wall area (perimeter × height). If your home has gable ends or dormers, add their triangular area (½ × base × height) to the total manually before ordering.
Using average sizes (21 sq ft per door, 15 sq ft per window) is accurate enough for material estimating and much faster than measuring every opening. For a final, no-waste order, measure your actual doors and windows and adjust.
Yes — vinyl siding is sold and installed in squares just like most other lap siding, so the same area, waste, and squares math applies. If you're installing James Hardie fiber cement planks instead, use the dedicated Hardie siding calculator, which accounts for plank length and exposure rather than squares.