A square is the unit siding is ordered in. Every 100 square feet is one square, which is 9.29 square meters, so a wall of 1,000 sq ft is 10 squares before anything else is added.
1 siding square = 100 sq ft
Squares = area ÷ 100 sq ft
Four numbers, not one
People use “how much siding” for four different quantities. Taking a 1,000 sq ft area of wall with a 10% allowance:
| What it is | Number |
|---|---|
| Measured wall area | 1,000 sq ft |
| Area with the allowance | 1,100 sq ft |
| Siding squares to order | 11 squares |
| Cartons at an example 150 sq ft each | 8 cartons |
The measured area is what you walked off. The allowance covers cuts and waste, and the squares round the result up to a whole unit. Cartons are a separate route, and they use the coverage on the carton, not 100 sq ft.
Squares do not round the way area does
Because a square is a whole ordering unit, any fraction rounds up. Here the area with allowance comes to exactly 11 squares, so 11 squares leaves nothing over; most walls do not come out whole, and the extra is part of the last square.
Metric
A square is defined in square feet, and 100 sq ft is 9.29 square meters. A 1,000 sq ft wall entered in metric as 92.9 sq m gives the same 11 squares, because the planner converts through one unit table.
What changes the estimate?
- Whether your supplier sells by the square or by the carton
- The allowance you add before converting
- Large openings you deduct, which change the area but not the unit
- The coverage on the carton, if you order that way
For the full quantity of a house, including gables and openings, see how much siding you need. Roofing uses the same 100 sq ft unit for roof surface, covered in what a roofing square is.