Siding Calculator
Squares and boxes of vinyl siding from your home's dimensions.
One story is 8 to 10 ft; two stories 17 to 19 ft.
10% standard; 15% for complex walls or diagonal-cut gables.
You need
13.5 squares
Waste included, openings not subtracted (standard practice). Add gable triangles separately.
- Boxes (2 squares each)
- 7 boxes
- Wall area
- 1,224 sq ft
Estimates only. Verify quantities before ordering.
How this is calculated
Wall area = 2 x (length + width) x wall height. Squares = area x (1 + waste) / 100. Boxes assume the common 2-squares-per-box packaging for vinyl siding. Gables are extra: add width x height / 2 for each.
Enter your home's footprint and the wall height from foundation to eaves, and this calculator returns the siding in squares (100 square feet each, the unit siding is sold and quoted in) and the equivalent boxes. Standard practice is not to subtract windows and doors: the offcuts around openings roughly cancel what the openings remove, and the extra is your insurance.
Gable ends add triangles on top of the rectangle this calculator measures. Each gable adds half of (gable width x gable height), so a 30 ft wide gable rising 8 ft adds 120 square feet. Add your gable areas to the calculated total, or fold them into the waste factor for a low-pitch roof.
Siding for common house sizes
Rows assume 10% waste, no opening subtraction, and exclude gables; add width x height / 2 per gable end.
| House | Squares | Boxes |
|---|---|---|
| 24 x 24 ft garage, 9 ft walls | 9.5 squares | 5 boxes |
| 40 x 28 ft ranch, 9 ft walls | 13.5 squares | 7 boxes |
| 48 x 28 ft ranch, 9 ft walls | 15.0 squares | 8 boxes |
| 40 x 28 ft two-story, 18 ft walls | 26.9 squares | 14 boxes |
| 50 x 30 ft two-story, 18 ft walls | 31.7 squares | 16 boxes |
Siding materials and what they cost to own
Vinyl is the cheapest to buy and install and needs essentially no maintenance, which is why it dominates. Its limitations are appearance up close, a tendency to fade unevenly on sun-facing walls, and brittleness in cold, where a thrown stone or a ladder foot cracks a panel. It also has to hang loose rather than being nailed tight, because it expands and contracts substantially with temperature.
Fiber cement holds paint far longer than wood, resists impact, and does not burn, at roughly two to three times the installed cost of vinyl. It is heavy and cutting it produces silica dust that requires a proper mask and a dust-collecting saw. Engineered wood sits between the two: lighter and easier to cut than fiber cement, and better looking than vinyl, but it needs its cut edges sealed and it is less forgiving of prolonged wetting.
Real wood siding, cedar or pine, remains the best-looking option and the most demanding, wanting refinishing every few years depending on exposure. Whatever the material, the wall behind it does the waterproofing: siding is a rain screen, not a seal, and the water-resistive barrier, flashing, and drainage plane underneath determine whether the wall survives.
Squares, courses, and exposure
Siding is sold and quoted by the square, meaning 100 square feet, the same unit roofing uses. Vinyl is boxed in squares; lap siding is sold by the piece and converted. When comparing quotes, confirm whether a price is per square or per square foot, because the factor of 100 between them makes an unremarkable quote look either absurd or irresistible.
For lap siding, the count depends on exposure, the amount of each board left visible after the next one overlaps it, not on the board width. A 8 and a quarter inch board with a 7 inch exposure covers 7 inches of wall per course. Manufacturers specify a minimum overlap, usually around an inch and a quarter, and the exposure has to be adjusted slightly across a wall so courses land neatly at window heads and sills rather than leaving a sliver at the top.
Order about 10 percent over the net wall area, and more on a house with many gables, dormers, or windows. Gable ends generate angled cuts where the offcut is rarely usable elsewhere, and each opening produces waste around it that the raw area calculation does not reflect.
The trim and accessories nobody budgets for
The panels are the cheap part of a siding order. Starter strip, J-channel around every window and door, outside and inside corner posts, undersill trim, utility trim, and finish trim add up quickly and are ordered by the linear foot, so they need their own takeoff. Running out of J-channel mid-wall is the most common reason a weekend siding job stops.
Fasteners are specific and not interchangeable. Vinyl needs roofing nails long enough to reach an inch into solid wood, driven in the center of the nailing slot and left about a thirty-second of an inch loose so the panel can slide. Nailing vinyl tight is the classic error and produces the wavy look you see on badly sided houses within a year or two of installation.
Add house wrap, flashing tape, and window and door flashing to the list. These are inexpensive relative to the siding and are the components that actually keep water out of the wall. Skipping the flashing above a window to save an afternoon is how a wall rots invisibly for a decade.
Common questions
What is a square of siding?
One square covers 100 square feet of wall. Vinyl siding is typically packaged two squares per box, and quotes from contractors and suppliers are almost always priced per square, which is why this calculator leads with that number.
Should I subtract windows and doors?
Usually no. The pieces cut away around openings are rarely reusable elsewhere on the wall, so the standard estimating practice is to measure walls as solid rectangles and let openings offset the cutting waste. Subtract only very large areas like a garage door wall.
How do I measure gables?
A gable is a triangle: its area is width times height divided by two. Measure the gable's base width and the vertical rise from the eave line to the peak, halve the product, and add one triangle per gable end. Steep roofs make surprisingly large gables, so measure rather than guess.
How much does the trim add?
J-channel around every opening and edge, starter strip along the bottom, corner posts, and utility trim under windows are all separate purchases, usually sold in 12 ft 6 in lengths. Count linear feet for each: perimeter of openings for J-channel, wall base for starter, and wall height times four for corners.