Siding Calculator
Enter the total wall length, the wall height, any gable ends and the area of doors and windows. The calculator adds waste and gives the siding squares to buy, plus a piece count if you know what one piece covers.
Last updated November 4, 2026
Add up every wall you are siding. For a whole house this is the perimeter.
Foundation to the eave.
A typical window is about 15 sq ft and an entry door about 21 sq ft.
10% is a common starting point; use more for many corners or angled cuts.
Exposed length × exposure from the product label. Leave blank to see squares only.
Result
16 squares of siding
| Measure | Value |
|---|---|
| Wall area | 1,440 sq ft |
| Area to cover | 1,440 sq ft |
| With 10% waste | 1,584 sq ft |
| Squares needed | 15.84 |
| Squares to buy (rounded up) | 16 |
Area method only. Trim, starter strips, corners and J-channel are bought separately, and cut layout can change the count. Confirm with your supplier.
Show the work
Formula: squares = (walls + gables − openings) × (1 + waste ÷ 100) ÷ 100 sq ft; gable = base × rise ÷ 2
- Walls: 160 ft × 9 ft = 1,440 sq ft.
- Area to cover: 1,440 + 0 − 0 openings = 1,440 sq ft.
- Waste: 1,440 × (1 + 10 ÷ 100) = 1,584 sq ft.
- Squares: 1,584 ÷ 100 sq ft per square = 15.84, rounded up = 16.
Result: 16 squares of siding
How the siding area is worked out
squares = (walls + gables − openings) × (1 + waste ÷ 100) ÷ 100 sq ft
gable = base × rise ÷ 2
Wall area is the total wall length times the wall height. Each triangular gable adds half of its base times its rise. Doors and windows are subtracted as one total. Waste is added on top of what is left, then the result is divided by 100 because one siding square covers 100 square feet of wall.
Squares are rounded up to a whole square, and pieces are rounded up from the area to buy divided by the coverage of one piece.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Choosing a waste percentage
Cuts at corners, windows and rooflines leave offcuts you cannot reuse. A simple rectangular house needs less waste than one with many corners or angled walls. The default of 10 percent is a common starting point, not a rule, so raise it if your layout is complicated.
What is not included
This is an area estimate. Trim, corner posts, starter strips, J-channel, house wrap and fasteners are bought separately and are not counted here. Check the coverage printed on your product and confirm the order with your supplier.
How to use the Siding Calculator
- Add up the length of every wall you are siding and enter it with the wall height.
- Enter the number of gable ends, with the base and rise of each.
- Enter the total area of doors and windows, and a waste percentage.
- Optionally enter the coverage of one piece to get a piece count.
- Read the squares to buy, then use Copy, Print or Share.
Worked example
A house with 160 feet of wall at 9 feet high and 10 percent waste covers 1,440 square feet, which becomes 1,584 square feet with waste, or 15.84 squares. You buy 16.
| Layout | Area to cover | With waste | Squares to buy |
|---|---|---|---|
| 160 ft × 9 ft, 10% waste | 1,440 sq ft | 1,584 sq ft | 16 |
| Same, 2 gables 30 × 8 ft, 150 sq ft openings | 1,530 sq ft | 1,683 sq ft | 17 |
| 100 ft × 8 ft, 60 sq ft openings, 12% waste | 740 sq ft | 828.8 sq ft | 9 |
Frequently asked questions
How much does one square of siding cover?
One square covers 100 square feet of wall. Siding is priced and sold this way, so squares are the unit to take to a supplier.
How do I measure a gable end?
Measure the base along the eave and the rise from the eave to the peak. The triangle area is half of the base times the rise.
Do I subtract every window and door?
Yes, add up their areas and enter the total. Very small openings can be ignored because they save little and leave extra for cuts.
How do I find the coverage per piece?
Multiply the exposed length by the exposure shown on the product label. A 12 foot piece with 8 inches showing covers 8 square feet.