How do I use this as a vinyl siding calculator?

Measure the same way for any material — the geometry does not change. What changes is how it is packaged. Vinyl is sold by the box and a box covers two squares, so the calculator converts your square footage into squares and then into boxes and rounds up, because you cannot buy part of a box. Fiber cement and engineered wood are sold by the plank instead, so for those the square figure is the one to take to the supplier. Vinyl also wants the higher waste allowance on a cut-up elevation, since every corner post and J-channel run costs you offcuts.

How many squares of siding do I need?

Divide your net wall area by 100 — a square is 100 square feet and it is the unit siding is quoted and sold in. A typical single-story ranch runs 10 to 13 squares and a two-story home 18 to 24, before waste. Add the waste allowance before ordering, not after: 10 percent on a simple rectangular elevation, up to 18 percent where there are dormers, bays and multiple corners.

How do you calculate square footage for siding?

Measure each wall's width and height and multiply them, then add the walls together. Gable ends are triangles, so multiply the width by the height of the peak above the eave and halve it. Subtract large openings like garage doors and picture windows, leave small windows in, then add 10 to 18 percent for waste depending on how cut-up the elevation is. Divide the final figure by 100 to get squares, which is how siding is sold.

How do you measure a gable end for siding?

A gable is a triangle, so its area is the width of the wall multiplied by the height from the eave line to the peak, divided by two. A 28-foot-wide gable rising 8 feet above the eave is 28 × 8 ÷ 2, or 112 square feet. Measuring it as a rectangle — a common mistake — doubles it. Gables also waste more material than flat walls because every course needs an angle cut at both ends.

Do you subtract windows and doors from siding square footage?

Large openings yes, small ones generally no. Estimators deduct garage doors, patio doors and picture windows at full size, but leave windows under about 10 square feet in the total. The reason is that the material cut out around a small window is mostly offcut that cannot be used elsewhere, so deducting it produces an order that comes up short. Subtracting every opening at full area is the most common way people under-order.

How many square feet is a square of siding?

One square is 100 square feet, in every material that uses the unit. Vinyl siding is usually cartoned in double squares, so one box covers 200 square feet. Fiber cement and engineered wood are more often sold by the piece, so you'll convert squares into planks using the board's exposure.

How much extra siding should I order for waste?

Ten percent on a simple boxy elevation, around fourteen on a house with gables or a dormer, and up to eighteen on something with many corners, steep pitches or staggered courses. Angle cuts are what drive it: a gable end leaves an offcut at both ends of every course, and most of those offcuts are too short to use anywhere else. Complex trim details and mitered corners push it higher still.

Does siding square footage include the soffit and fascia?

No. Soffit, fascia, corner posts, J-channel and starter strip are all bought separately and measured differently — soffit by the area of the overhang, the rest by the linear foot. The square footage figure covers the wall surface only. Corner trim is the one most often forgotten, which is why this calculator works it out from the number of outside corners and their height.

Siding Calculator: Square Footage, Squares & Boxes

Measure wall by wall, with gables and dormers as their own shapes rather than something you work out on the back of an envelope. It deducts openings the way an estimator actually does, adds a waste allowance matched to how cut-up your house is, and gives you squares, boxes and linear feet of corner trim.

Walls and gables

Width (ft)Height (ft)How many

A plain wall. Width × height. = 1,440 sq ft

Width (ft)Height (ft)How many

A plain wall. Width × height. = 1,008 sq ft

Width (ft)Peak height (ft)How many

The triangle above the eave. Width × peak height ÷ 2. = 224 sq ft

Windows and doors

Width (ft)Height (ft)How many

15 sq ft each · deducted, 210 sq ft total

Width (ft)Height (ft)How many

21 sq ft each · deducted, 42 sq ft total

Which openings to subtract

Only openings over 10 sq ftWhat estimators actually do. The offcuts around a small window are waste you pay for either way.Every opening, at full sizeGives the smallest number. Order from it and you will be short.None of themThe most conservative. Sensible on a very cut-up elevation.

Waste and trim

Simple — 10%A boxy elevation: four corners, few openings, one roof line. 10% is the trade default.Moderate — 14%Gable ends, a dormer or two, an offset bay. Angle cuts on gables waste more than square cuts.Complex — 18%Many corners, multiple gables, steep pitches, turrets or staggered courses. Every angle cut leaves an offcut too short to use.

Outside cornersCorner height (ft)

Corner posts are sold by the linear foot, separately from the siding. Forgetting them is the most common second trip to the supplier.

Siding to order

2,758.8 sq ft

That is 28 squares — or 14 boxes if you are buying vinyl, which is cartoned in double squares.

Gross wall areaEvery surface, before anything comes off.: 2,672 sq ft
Openings measured: 252 sq ft
Deducted: −252 sq ft
Net wall areaThe figure to put into a cost calculator.: 2,420 sq ft
Waste allowance14% for moderate work.: +338.8 sq ft
Corner trimBought separately from the siding.: 72 linear ft

Order from the gross-plus-waste figure, price from the net. They are different numbers doing different jobs. A supplier needs to know what to put on the truck, including the pieces that end up in the skip. A cost estimate is about the wall you are actually covering.

Price 2,420 sq ft by material →Take this number straight into the siding cost calculator, for any of the eight materials.

Measure to the outside of corner boards and from the bottom of the starter strip to the top of the wall. A planning estimate, not a supplier take-off — on a complex elevation, have the number checked before you buy.

Why it doesn't subtract every window

This is the decision that separates a number you can order from and a number that leaves you short, and almost every siding calculator gets it wrong by being too generous.

When you side around a window, you cut a piece to fit above it, a piece below, and two short returns at the sides. The material you cut out of the opening mostly does not come back as usable stock — it is offcut. So the opening costs you wall area you never cover, but it does not save you the material.

Estimators handle this by deducting only openings big enough that the saving is real: garage doors, patio sliders, picture windows — anything over roughly 10 square feet. A standard 3 × 5 window stays in the total. Subtracting every opening at full area is the single most common reason a siding order comes up short, and it compounds with an optimistic waste factor.

Waste is about angles, not carelessness

A waste allowance is not padding for mistakes. On a rectangular wall, siding runs wall-to-wall and the only waste is the last piece in each course. On a gable end, every single course needs an angle cut at one or both ends, and the triangle you cut off is almost never the right shape for anywhere else on the house.

That is why the allowance scales with complexity rather than with house size. Ten percent covers a boxy ranch. A house with two gable ends and a dormer is closer to fourteen. Multiple rooflines, steep pitches, staggered courses or a turret push it to eighteen and beyond — and on those elevations it is worth having a supplier do a proper take-off rather than trusting any calculator, including this one.

Whole-house ballparks

If your total lands far outside these, re-check your wall heights — measuring to the eave instead of the top of the wall is the usual culprit.

Typical siding square footage by house type
House	Siding area	Squares
Single-story ranch, ~1,200 sq ft floor	1,000–1,300 sq ft	10–13
Single-story with gable ends, ~1,600 sq ft floor	1,300–1,600 sq ft	13–16
Two-story colonial, ~2,000 sq ft floor	1,800–2,400 sq ft	18–24
Two-story with dormers, ~2,600 sq ft floor	2,400–3,000 sq ft	24–30
Split level, ~1,800 sq ft floor	1,600–2,000 sq ft	16–20

Siding area runs well ahead of floor area on almost every house, which surprises people. A two-story home has twice the wall for the same footprint, and gables add area no floor plan accounts for.

Turning square feet into a price

Order from the gross-plus-waste figure and price from the net — they are different numbers doing different jobs. A supplier needs to know what goes on the truck, including what ends up in the skip. A cost estimate is about the wall you actually cover.

The net figure is the one to carry over. Price it by material in the cost calculator, or if you already have a bid, check whether the area on it is plausible — a quote built on a wall area far from your own measurement is worth a conversation before it is worth a signature.

Keep going

Siding Cost CalculatorTake your square footage straight into a price, for any of the eight materials.How to Measure SidingThe tape-measure method, step by step, if you'd rather do it by hand.Quote-Fairness CheckAlready have a quote? See whether the area they used is plausible.Siding Replacement CostWhat tear-off, sheathing repair and disposal add on top.

Frequently asked questions

How do I use this as a vinyl siding calculator?: Measure identically — geometry does not change by material. Vinyl is sold by the box, and a box covers two squares, so the calculator rounds your squares up into boxes. Fiber cement and wood are sold by the plank, so take the square figure instead.
How many squares of siding do I need?: Net wall area ÷ 100. A square is 100 sq ft. Roughly 10–13 squares for a single-story ranch and 18–24 for a two-story, before waste.
How do you calculate square footage for siding?: Width × height for each wall, added together. Gables are triangles — width × peak height ÷ 2. Subtract large openings, add 10–18% waste, divide by 100 for squares.
How do you measure a gable end for siding?: Width × height to the peak ÷ 2 — it's a triangle. A 28 ft gable rising 8 ft is 112 sq ft, not 224. Treating it as a rectangle is the usual error.
Do you subtract windows and doors from siding square footage?: Large ones yes, small ones no. The offcuts around a small window are waste you pay for either way — deducting every opening is how people end up short.
How many square feet is a square of siding?: 100 square feet. Vinyl is boxed in double squares, so a carton covers 200.
How much extra siding should I order for waste?: 10% for a boxy house, ~14% with gables or dormers, up to 18% for many corners and steep pitches. Angle cuts drive it — offcuts from gable courses are usually unusable.
Does siding square footage include the soffit and fascia?: No — soffit, fascia, corner posts and J-channel are separate items measured by the linear foot. This figure is wall surface only.