How to use this siding calculator
- Add up the length of all exterior walls.
- Enter the wall height from the foundation to the eaves.
- Add each gable (the triangle under a gable roof) with its base width and peak height.
- Count doors and windows; they are subtracted using average sizes (21 and 15 sq ft).
Example
A house with 140 ft of walls, 9 ft high, two 30 ft wide gables and 12 openings needs 14.1 squares of siding with 10% waste (1,406 sq ft (130.6 m²)).
What to know before you buy
Popular siding materials
Vinyl siding is affordable and low-maintenance. Fiber cement is more durable, fire-resistant and can be painted. Wood siding offers a natural look but needs regular maintenance. Engineered wood and metal are other durable options.
Measuring your walls
Measure each wall's length and height and add them, or use the perimeter of the house times the wall height. Measure gables separately as triangles. Add trim pieces (corners, J-channel, soffit) by the linear foot.
Siding for rectangular houses (9 ft walls, 2 gables 7 ft high, 10% waste)
| House footprint | Siding needed | Area (with waste) |
|---|---|---|
| 30 × 40 ft | 14.1 squares | 1,406 sq ft (130.6 m²) |
| 30 × 50 ft | 16 squares | 1,604 sq ft (149 m²) |
| 35 × 50 ft | 17.4 squares | 1,742 sq ft (161.8 m²) |
| 40 × 60 ft | 20.8 squares | 2,077 sq ft (193 m²) |
Formula
Area = wall length × height + gables × (width × height ÷ 2) − openings. Siding is sold by the square (100 sq ft).
Tips from the pros
- Order trim, J-channel, corner posts and starter strips separately; they are sold by the piece.
- Install a weather-resistant barrier (house wrap) before new siding.
- Keep leftover siding: matching colors years later can be difficult.
Common mistakes to avoid
- Forgetting the gable triangles, which add a lot of area on steep roofs.
- Installing vinyl siding nailed tight; it must be able to expand and contract.
Frequently asked questions
How much extra siding should I order?
About 10% for simple houses and up to 15% for houses with many corners and openings.
What is a square of siding?
Enough siding to cover 100 square feet of wall.
How many squares of siding for a 2,000 sq ft house?
A two-story 2,000 sq ft house often needs 20–25 squares, but measure the walls for an accurate number.
Do I subtract windows from siding estimates?
Subtract large openings like garage doors; for small windows many installers do not, because of extra cutting waste.