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This siding calculator estimates how much siding you need to cover the outside of a house. Enter the length and height of the walls, the size of the gables and the number of doors and windows, and it calculates the net area in square feet and squares, plus the number of vinyl siding boxes and panels to order.
How to Use the Siding Calculator
- Measure the total length of all exterior walls (the house perimeter).
- Measure the wall height from the bottom of the siding to the eaves.
- Enter the number of gables and the base width and height of a typical gable.
- Enter the number of doors and windows, and a waste allowance (10% for simple houses, 15% for complex ones).
Siding Formula
Wall area = Perimeter × Wall height
Gable area = ½ × Gable width × Gable height × Number of gables
Squares = (Wall area + Gable area − Openings) × (1 + waste %) ÷ 100
Siding is sold by the square, which covers 100 sq ft. The calculator counts each door as 21 sq ft (3 × 7 ft) and each window as 15 sq ft (3 × 5 ft); measure garage doors and large windows separately for better accuracy.
Example
A house with 140 ft of walls, 9 ft high, two 30 ft wide gables 7 ft tall, 2 doors and 10 windows has 1,260 + 210 − 192 = 1,278 sq ft of siding. With 10% waste you need about 1,406 sq ft, or 14.1 squares (8 boxes of vinyl siding).
Siding Coverage by Type
| Siding | How it is sold | Typical coverage |
|---|---|---|
| Vinyl (double 4 in) | Boxes of 2 squares | 12 ft 6 in panel covers about 8.3 sq ft |
| Fiber cement lap | Planks | 8.25 in plank at 7 in exposure: about 7 sq ft per 12 ft plank |
| Wood clapboard | Linear feet | Depends on board width and exposure |
| Cedar shingles | Bundles | Typically 25 sq ft per bundle at 7 in exposure |
Don’t Forget Trim and Accessories
- J-channel around windows and doors (measure the perimeter of each opening).
- Outside and inside corner posts (one per corner, the height of the wall).
- Starter strip along the bottom of every wall (equal to the perimeter).
- Soffit, fascia and house wrap, which are calculated separately.
Replacing the roof at the same time? Use the roofing calculator and the roof replacement cost calculator.
Frequently Asked Questions
How do I calculate how much siding I need?
Multiply the house perimeter by the wall height, add the gable triangles, subtract doors and windows, add 10–15% waste and divide by 100 to get squares.
How many square feet are in a square of siding?
One square of siding covers 100 square feet.
How many squares of siding for a 2,000 sq ft house?
It depends on wall height and shape, but a two-story 2,000 sq ft home typically needs about 20–30 squares of siding.
How much waste should I add for siding?
Add about 10% for simple rectangular houses and 15% or more for houses with many corners, gables and windows.
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