How do I calculate siding square footage?

Multiply the length of each exterior wall by its height, add the walls together, then subtract large openings like garage doors and picture windows. Add gable triangles (½ × base × height). Most people add about 10% for waste and trim.

How many square feet of siding does an average house need?

A typical single-story home has about 1,000 to 1,300 square feet of siding, and a two-story home about 1,800 to 2,400. It's a rough shortcut — measuring your own walls is more accurate.

What is a 'square' of siding?

A square is 100 square feet of siding — the unit contractors and suppliers use to order and price material. A 2,900-square-foot home is 29 squares. Converting your square footage into squares makes it easy to compare quotes and material orders.

How much extra siding should I order for waste?

Add about 10% for a simple home with straightforward walls, and up to 15% for complex rooflines, many corners, dormers, or diagonal cuts. Ordering a little extra also gives you matching material for future repairs, which is valuable if the color is later discontinued.

How to Measure Siding Square Footage

Independent research · Last reviewed August 2026

The short answer

Multiply each exterior wall's length by its height, add the walls together, subtract large openings like garage doors, and add gable triangles (½ × base × height). Add about 10% for waste and trim. As a shortcut, a single-story home is ~1,000–1,300 sq ft; a two-story ~1,800–2,400.

Step by step

Measure each wall — length × height for every flat rectangular section.
Add the rectangles together for the base wall area.
Subtract big openings — garage doors, picture windows (skip small windows; they roughly offset waste).
Add gables — for each triangular gable, ½ × base × height.
Add ~10% waste for cuts, trim, and overlap.

A worked example

Take a simple two-story rectangular home, 40 ft wide and 30 ft deep, with 18 ft walls and two gable ends:

Front & back walls: 40 ft × 18 ft × 2 = 1,440 sq ft
Side walls: 30 ft × 18 ft × 2 = 1,080 sq ft
Two gables: ½ × 30 ft × 8 ft × 2 = 240 sq ft
Subtotal: 2,760 sq ft
Subtract a garage door (16 × 8): −128 sq ft → 2,632 sq ft
Add 10% waste: ≈ 2,900 sq ft to order

Small windows and doors are usually left in to offset cutting waste; only subtract the big openings. Complex rooflines, dormers, and lots of corners push the waste factor toward 15%.

Squares, boxes, and how siding is sold

Contractors often talk in “squares” — one square = 100 square feet. Our 2,900 sq ft example is 29 squares. Vinyl is sold by the box (a couple of squares each), fiber cement and wood by the piece or lineal foot, so your square-foot number is the starting point a supplier converts into an order. Knowing it also lets you catch a quote that's measuring a wildly different area than your home actually has.

Put the number to work

Once you have a square-foot figure, drop it into the cost calculator for an installed estimate, or into the quote-fairness checker to sanity-check a bid. Contractors will measure precisely, but your own number keeps their quote honest.

Frequently asked questions

How do I calculate siding square footage?: Multiply each wall's length by height, add them, subtract big openings, add gables (½ × base × height), then add ~10% for waste.
How many square feet of siding does an average house need?: Roughly 1,000–1,300 sq ft for a single-story, 1,800–2,400 for a two-story — but measuring is more accurate.
What is a 'square' of siding?: 100 square feet of siding — the unit used to order and price it. A 2,900 sq ft home is 29 squares.
How much extra siding should I order for waste?: About 10% for a simple home, up to 15% for complex ones — and the extra doubles as matching stock for future repairs.