How it works
The formula
area = wall length × height + each gable ½ × width × height − ½ of large openings
squares = area × (1 + waste) ÷ 100 · panels = area ÷ sq ft per panel
squares = area × (1 + waste) ÷ 100 · panels = area ÷ sq ft per panel
- The method is the Vinyl Siding Institute's: a square is 100 sq ft; ordinary windows and doors aren't subtracted, which leaves an allowance for waste; only half of very large openings like garage doors comes off.
- VSI says to add extra for waste depending on the roof pitch and the house, without a number; the 10% default is ours, so change it for a complicated house.
- A double 4 in panel (8.33 sq ft) is 12 ft 6 in long with an 8 in exposure; a double 5 in panel (10 sq ft) is 12 ft with 10 in. Starter strip and J-channel come in 12 ft 6 in lengths and corner posts in 10 ft (Kaycan's trim specifications); check your brand.
- VSI measures starter strip around the whole base of the house; each corner gets a post as tall as the wall.
Siding by house size
| Walls | Squares | Double 4 in panels |
|---|---|---|
| 100 ft × 8 ft | 11.0 | 132 |
| 140 ft × 9 ft | 16.0 | 193 |
| 180 ft × 9 ft | 20.0 | 240 |
| 220 ft × 18 ft | 45.7 | 549 |
With two 28 × 7 ft gables and 10% extra.
Questions people ask
How many squares of siding do I need?
Multiply the wall length around the house by the height, add each gable as half its width × its height, divide by 100 and add extra for waste. A 140 ft × 9 ft house with two 28 × 7 ft gables is 16.0 squares with 10% extra.
Do I subtract windows and doors?
Usually not: the Vinyl Siding Institute leaves them in as the allowance for waste and cutting. Take off half of very large openings, like a garage door or sliding patio doors.
How many panels are in a square?
About 12 double 4 in panels or 10 double 5 in panels; siding usually comes 2 squares to a carton.