Siding Calculator
This siding calculator totals every wall and gable on your house, subtracts the doors and windows, and turns the answer into squares, square feet, and 12-foot vinyl panels. Enter each wall’s width and height in feet or meters, open the advanced panel to add walls three through six and up to four gables, and the result updates with a separate 10% waste line.
Siding to order
11.3squares
- Net siding area1,027 sq ft
- With 10% waste — order1,130 sq ft
- 12-ft vinyl panels (8 sq ft each)142 panels
Formulas last reviewed on .
How the siding area is calculated
Every wall is a simple rectangle, and every gable is a triangle worth half its enclosing rectangle. The calculator adds them all up, then pulls the openings back out:
squares to order = net area × (1 + waste) ÷ 100
The deductions are industry-standard averages: 21 square feet per door (a 3 × 7 entry door) and 15 square feet per window. They’re approximations — a bay window or patio slider is bigger — but over a whole house they wash out. For a garage door, measure it and shorten that wall’s width instead, because 100+ square feet is too much to average away.
A square is siding’s selling unit: 100 square feet. The 10% waste allowance is editable and covers end cuts, laps, and the offcuts you can’t reuse. The panel count divides the with-waste area by one panel’s coverage — a 12-foot vinyl panel with 8-inch exposure covers roughly 8 square feet, and that figure is editable in the advanced panel because profiles vary.
Worked example: re-siding a 40 × 24 ranch
Picture a single-story ranch, 40 feet long and 24 feet deep, with 8-foot walls, a gable at each end, one entry door, and eight windows. Those are the calculator’s default inputs, so the result box above shows every number in this walkthrough.
- Walls: two long walls at 40 × 8 = 640 sq ft, two end walls at 24 × 8 = 384 sq ft. Subtotal: 1,024 sq ft.
- Gables: each end gable is 24 feet wide and rises 6 feet to the peak: 24 × 6 ÷ 2 = 72 sq ft. Two of them add 144 sq ft. Running total: 1,168 sq ft.
- Openings: one door (−21) and eight windows (−120) bring the net siding area to 1,027 sq ft.
- Waste: 1,027 × 1.10 = 1,129.7, so order 1,130 sq ft — 11.3 squares.
- Panels: 1,129.7 ÷ 8 = 141.2, rounded up to 142 twelve-foot vinyl panels.
Order the 11.3 squares as twelve if your supplier only sells whole squares — the leftovers matter, because vinyl lots vary slightly in color and a matching repair panel five years from now is worth having in the garage.
How many squares of siding do I need for my house?
The table below runs the formula for typical footprints: 8-foot walls per story, 6- to 7-foot gable peaks on both ends, and the listed door and window counts. All rows include 10% waste, with panels figured at 8 square feet each.
| House | Doors / windows | Net area (sq ft) | Squares (10% waste) | Vinyl panels |
|---|---|---|---|---|
| 24 × 24 one-story | 1 / 6 | 801 | 8.9 | 111 |
| 30 × 24 one-story | 1 / 8 | 867 | 9.6 | 120 |
| 40 × 24 one-story | 1 / 8 | 1,027 | 11.3 | 142 |
| 50 × 26 one-story | 2 / 10 | 1,193 | 13.2 | 165 |
| 32 × 24 two-story | 1 / 10 | 1,765 | 19.5 | 243 |
| 40 × 28 two-story | 2 / 14 | 2,120 | 23.4 | 292 |
Note how a second story roughly doubles the wall area but the gables stay the same — that’s why the 32 × 24 two-story needs far more siding than the bigger-footprint 50 × 26 ranch. Your own walls, gables, and openings will differ, so treat these as sanity checks and run your real measurements above.
Frequently asked questions
What is a square of siding?
A square is 100 square feet of coverage — the unit siding is priced and sold by, same as roofing. Vinyl siding typically comes in cartons of about two squares (roughly 24 twelve-foot panels), so an 11.3-square job means ordering six cartons. Fiber cement and engineered wood are usually sold per piece instead, which is why the calculator also gives you the raw square footage.
How do I measure a gable end for siding?
Measure the gable’s width where the triangle starts — the top of the regular wall — and the vertical rise from that line to the peak, then take half of width × height. A triangle is exactly half its enclosing rectangle, so a 24-foot gable rising 6 feet is 72 square feet. If you can’t reach the peak, estimate the rise from the roof pitch: half the width × (pitch ÷ 12).
How much extra siding should I order for waste?
Use 10% on a plain rectangular house. Bump it to 12–15% when the layout fights you: lots of corners, dormers, or gable walls full of angled cuts. Horizontal siding also loses material to staggered end joints — you offset each course’s seams from the one below, and the short offcuts that would line up with an existing seam become scrap instead of starters.
Do I subtract doors and windows when calculating siding?
Yes — this calculator deducts 21 square feet per door and 15 per window, which are stock estimating averages. That’s deliberate rounding, not precision: trimming around openings eats some of what you “save.” The one opening you should never average is a garage door; measure it and subtract its real area by shortening that wall’s width, since a 16 × 7 door is 112 square feet on its own.
How much house wrap do I need under new siding?
A standard roll of house wrap is 9 × 150 feet — about 1,350 square feet. Size it against your gross wall and gable area before subtracting openings, because the wrap goes over everything and gets cut out afterward. The 40 × 24 ranch above has 1,168 gross square feet, so one roll covers it with overlap to spare; the two-story examples need two.
These results are planning estimates only — verify quantities with your supplier and local building code before you buy or build. See our terms of use.