How to use the siding calculator
- Measure around the outside of the house at the base of the walls and enter the total. Leave out walls you aren't siding, like a garage that stays brick.
- Enter the wall height from the bottom of the siding to the eaves.
- For each triangular gable end, enter its width and its height from the eaves line to the peak. Use 0 gables for a hip roof.
- Add up the area of doors and windows. Many pros skip this and treat it as extra, which also covers trim cuts.
Siding formula
wall area = distance around × wall height
gable area = gables × width × height ÷ 2
squares = (wall area + gable area − openings) × (1 + waste) ÷ 100
Siding is sold by the square, which covers 100 sq ft. A box of vinyl siding usually holds 2 squares. Fiber cement and wood lap siding come in 12 ft planks, and each plank covers its length times the exposure (the part left showing): an 8 1/4 in plank with 7 in exposure covers 7 sq ft.
Siding for common house sizes
Single-story box house with two gable ends on the short sides and a 6/12 roof pitch, 300 sq ft of doors and windows taken out, 10% extra.
| House | Gross sq ft | Squares | Vinyl boxes | Lap planks (7 in) |
|---|---|---|---|---|
| 30 × 24 ft, 8 ft walls | 1,008 | 7.8 | 4 | 112 |
| 40 × 28 ft, 8 ft walls | 1,284 | 10.8 | 6 | 155 |
| 50 × 30 ft, 9 ft walls | 1,665 | 15.0 | 8 | 215 |
| 60 × 30 ft, 9 ft walls | 1,845 | 17.0 | 9 | 243 |
| 40 × 30 ft, 18 ft walls | 2,745 | 26.9 | 14 | 385 |
Don't forget the trim
- Outside and inside corner posts: one per corner, as tall as the wall.
- J-channel: around every window and door, and along the gable rakes. Measure the perimeter of each opening and add 10%.
- Starter strip: the distance around the house at the bottom of the wall.
- Soffit and fascia: sold separately, by the length of the eaves.
- House wrap: about the same area as the siding. One 9 × 100 ft roll covers 900 sq ft.
Frequently asked questions
How many square feet are in a square of siding?
One square of siding covers 100 sq ft of wall. Siding is priced and sold by the square.
How many squares of siding do I need for a 2,000 sq ft house?
Floor area and wall area are different, but a typical 2,000 sq ft two-story house has around 2,000 to 2,500 sq ft of wall, so plan on roughly 20 to 28 squares with 10% extra. Measure the walls for a real number.
How many pieces of vinyl siding are in a box?
A box of vinyl siding usually covers 2 squares (200 sq ft). That is commonly 16 to 24 panels, depending on the profile and length.
How much extra siding should I buy?
Add 10% for a simple rectangular house and 15% for one with many corners, gables, dormers or bump-outs.