Siding Calculator
To estimate siding, find the wall area (perimeter × height), add 10–15% for waste, then divide by 100 for squares. Multiply the area by the installed price per square foot — vinyl runs about $4–$8 and fiber-cement $6–$13. A 40×30 ft home with 9 ft walls needs about 1,386 ft² of siding.
- 1 siding square
- 100 ft²
- Typical waste
- 10–15%
- Cheapest type
- Vinyl
Your measurements
Enter your measurements
Fill in the fields to see your estimate.
The formula
Siding (ft²) = Perimeter × Height × (1 + waste %); Squares = area ÷ 100How to calculate it manually
- 1
Measure the perimeter
Add the length of all exterior walls (2 × (length + width) for a rectangle).
- 2
Multiply by wall height
This gives the gross wall area in square feet.
- 3
Add waste
Add 10% for simple walls, 15% for homes with many corners and openings.
- 4
Convert to squares
Divide by 100. Siding is ordered and priced by the square.
Example calculation
A 40 ft × 30 ft home with 9 ft walls: perimeter 140 ft × 9 = 1,260 ft² × 1.10 ≈ 1,386 ft² (≈ 13.9 squares).
Siding cost by material
Installed cost per square foot, including materials and labor.
| Material | Cost per ft² (installed) | Lifespan | Best for |
|---|---|---|---|
| Vinyl | $4 – $8 | 20–40 yrs | Budget, low maintenance |
| Fiber-cement | $6 – $13 | 30–50 yrs | Durability, fire zones |
| Engineered wood | $5 – $11 | 20–30 yrs | Wood look, lighter |
| Brick veneer | $10 – $20 | 75+ yrs | Premium, longevity |
Common siding estimating mistakes
Not subtracting large openings
Big windows, garage doors, and entries reduce the siding area — but keep the waste factor for cuts around them.
Forgetting trim and accessories
J-channel, corner posts, starter strip, and house wrap add to the order and the budget.
Skipping house wrap
A weather-resistant barrier behind the siding prevents moisture damage and drafts.
Underestimating gables
Triangular gable walls add area that a simple perimeter × height misses — measure them separately.
Frequently asked questions
Related calculators
Ready to start your siding project?
Run the numbers above, then explore related tools and guides to plan every step.