Siding Calculator
Enter your house's length, width, wall height, and gable ends (or a wall area) to get squares of siding to order, with the Vinyl Siding Institute's 10% waste allowance.
Your results
Squares to order
– squares
- Cartons
- – cartons
Check the highlighted fields to see your results.
Area
- Walls
- – sq ft
- Gable ends
- – sq ft
- Openings deducted
- – sq ft
- Area to side
- – sq ft
Order
- Area with waste
- – sq ft
- Squares before rounding up
- – squares
Estimates only. Check quantities with your supplier and local codes before you buy or build. See our Disclaimer.
Last updated: · By Drew Kessler
How it works, sources, and FAQ
What it calculates and who it’s for
What it estimates and who it is for
This calculator estimates how much vinyl or fiber-cement siding to order for a house: the area of the four walls, plus the triangular gable ends under a gable roof, plus a waste allowance, rounded up to whole squares. Siding is sold by the square (100 sq ft). It’s for homeowners pricing out a re-side, or checking a contractor’s material count. It covers the siding panels only; roofing and paint have their own calculators.
How to use
Step by step
- Measure the house: the length, the width, and the wall height from the foundation to the eaves. Or switch to entering a wall area you already have.
- Count the gable ends you’ll side (2 on a simple gable roof, 0 on a hip roof) and enter the gable height from the eaves to the peak.
- Deduct openings only if you want to. The Vinyl Siding Institute’s method leaves windows and doors in as part of the waste allowance.
- Enter carton coverage from the label to get a carton count.
- Read the squares to order.
The formula
Every variable and unit
- Walls (sq ft) = 2 × (House length + House width) × Wall height
- Gable ends (sq ft) = Number of gables × (House width × Gable height ÷ 2)
- Area to side (sq ft) = Walls + Gable ends − Openings deducted
- Area with waste (sq ft) = Area to side × (1 + Waste % ÷ 100)
- Squares = Area with waste ÷ 100, rounded up
- Cartons = Area with waste ÷ Coverage per carton, rounded up
The 10% waste default and the 100 sq ft square both come from the Vinyl Siding Institute’s installation manual, which says to add 10% to all material estimates.
Worked example
Real numbers, worked by hand
A 40 × 30 ft house with 9 ft walls, two gable ends 7.5 ft high, no openings deducted, 10% waste, cartons of 200 sq ft:
- Walls: 2 × (40 + 30) × 9 = 1,260 sq ft
- Gables: 2 × (30 × 7.5 ÷ 2) = 225 sq ft
- Area to side: 1,260 + 225 = 1,485 sq ft
- With waste: 1,485 × 1.10 = 1,633.5 sq ft
- Squares: 1,633.5 ÷ 100 = 16.34, rounded up to 17 squares
- Cartons: 1,633.5 ÷ 200 = 8.17, rounded up to 9 cartons
How to read your results
Rounding and buying tips
- Squares to order is rounded up to a whole square. Siding is often sold in cartons of 1 or 2 squares; enter the coverage from the label to see cartons.
- Area shows each part of the estimate so you can check the walls and gables separately.
- Trim, starter strip, J-channel, corner posts, soffit, and fasteners are ordered separately by the linear foot; this calculator doesn’t estimate them.
Assumptions and limits
What this estimate does not cover
- The house is a rectangle with walls of one height, and each gable end is a simple triangle across the house width. Dormers, bump-outs, and second-story walls need their own areas added; enter a total wall area instead if that’s easier.
- Openings are not deducted by default, following the VSI estimating method. Deducting them gives a tighter number with less spare material.
- The 10% waste comes from the VSI manual for vinyl siding. Fiber-cement and other products have their own instructions; check them.
- Confirm quantities with your supplier and follow the manufacturer’s installation instructions and local codes.
FAQ
4 questions
How many squares of siding do I need?
Add up the wall area and gable area in square feet, add 10% for waste, and divide by 100. A 40 × 30 ft house with 9 ft walls and two 7.5 ft gables needs 17 squares.
How do I measure a house for siding?
Measure each wall’s length and the height from the foundation to the eaves. For a gable end, measure the width and the height from the eaves to the peak, and take half of width × height for the triangle.
Should I subtract windows and doors?
The Vinyl Siding Institute’s method doesn’t, because the extra covers waste around the openings. Deduct big openings like garage doors if you want a tighter estimate.
What is a square of siding?
100 sq ft of wall coverage. A carton is often labeled in squares, such as 2 squares (200 sq ft).
Squares for common house sizes
Reference
All rows use two gable ends with a 6/12 roof pitch (gable height = width ÷ 4), no openings deducted, and 10% waste.
| House (ft) | Wall height (ft) | Walls (sq ft) | Gables (sq ft) | With 10% (sq ft) | Squares |
|---|---|---|---|---|---|
| 30 × 24 | 8 | 864 | 144 | 1,108.8 | 12 |
| 40 × 30 | 9 | 1,260 | 225 | 1,633.5 | 17 |
| 50 × 30 | 9 | 1,440 | 225 | 1,831.5 | 19 |
| 60 × 40 | 10 | 2,000 | 400 | 2,640 | 27 |
Sources
2 dated sources
- Vinyl Siding Installation Manual, Estimating Required Materials (Vinyl Siding Institute, 2022 edition, hosted by the Polymeric Exteriors Coalition): squares of 100 sq ft, gable area, add 10% for waste (accessed Nov 11, 2026)
- Vinyl Siding Installation Manual, updated December 2007 (Vinyl Siding Institute): same estimating method and 10% waste factor (accessed Nov 11, 2026)