How Much Siding Do I Need? (Squares Formula + Chart)
Part of Decks, Fences & Roofing
Quick answer
Multiply your total wall perimeter by the wall height, add gable areas, subtract doors and windows, add about 10% waste, then divide by 100 to get squares. A 1,260 ft² house is about 13.9 squares — 7 boxes of vinyl.
Siding is ordered in squares, where one square covers 100 square feet of wall. The whole job is just measuring your wall area, allowing for waste, and dividing by 100 — then converting squares to the boxes, planks or panels your product comes in.
The formula
Squares = (perimeter ft × height ft + gables − openings) × (1 + waste) ÷ 100
- Perimeter × height = the main wall area.
- Gables and dormers: each triangle is base × height ÷ 2.
- Openings: subtract about 21 ft² per door and 15 ft² per window.
- Waste: add 10% (simple walls) up to 15% (cut-up walls or shakes).
Squares by wall area (with 10% waste)
| Net wall area | Squares | Vinyl boxes (2 sq) |
|---|---|---|
| 800 ft² | 8.8 | 5 |
| 1,200 ft² | 13.2 | 7 |
| 1,600 ft² | 17.6 | 9 |
| 2,000 ft² | 22.0 | 11 |
| 2,400 ft² | 26.4 | 14 |
Squares to pieces
- Vinyl: 1 box = 2 squares (200 ft²). Boxes = squares ÷ 2, rounded up.
- Lap (fiber cement / wood): coverage per plank = exposure ÷ 12 × plank length. A 12 ft plank at 7" exposure covers 7 ft².
- Panel / board & batten: a 4×8 sheet covers 32 ft². Sheets = area ÷ 32.
Order trim separately — starter strip, J-channel, inside/outside corner posts and fasteners aren't part of the field squares. Add corners by the each and J-channel by the linear foot of openings and edges.
FAQs
What is a square of siding?
A square equals 100 square feet of wall coverage — the unit siding is sold and priced in. 2,000 ft² of wall is 20 squares before waste.
How many squares of siding for a 1,500 sq ft house?
Most single-story 1,500 ft² homes have 1,200–1,600 ft² of wall, so about 13–18 squares after openings and 10% waste. Measure your actual walls for an exact count.
How many boxes of vinyl siding in a square?
Vinyl is sold the other way around — one box holds 2 squares (200 ft²). So you need half a box per square, and boxes = squares ÷ 2 rounded up.