How much siding do I need for a 1,200 square foot house?

About 11 squares for a single storey 30 by 30 house with a 9 foot eave and 150 square feet of openings: the walls are 1,080 square feet, less the openings is 930, and 10% wastage takes it to 1,023, which is 11 squares. The floor area of the house is not the number to use — a 1,200 square foot single storey and a 1,200 square foot two storey have very different wall areas, and only the wall area matters here.

What is a square of siding?

One hundred square feet of wall, and it is a definition rather than a package size — unlike a bundle of shingles or a box of flooring, a square of siding is always exactly 100 square feet whatever you buy. That is why this page does not treat siding as a coverage product with a range: there is nothing to vary. What does vary is how much product it takes to cover a square, and that is the exposure.

What is the exposure on vinyl siding?

Exposure width is how much of each course you see once the lap above it is in place — the vertical height one panel adds to the wall. A double 4 panel has two 4 inch laps formed into it, so it covers 8 inches; a triple 3 covers 9; a single 4 covers 4. The exposure is printed on the carton, and it is the single input that changes the order most: halving it nearly doubles the panels for the same wall.

Why do the squares and the panels not match up?

Because they measure different things and are rounded up separately. The square count is the wall area with wastage, divided by 100; the panel count is the same area divided by the area of one panel as it is actually laid. The panel count is the higher of the two in product terms because every course ends in a cut and the off-cut rarely fits the next course, so the panels you buy always cover a little more wall than the wall you have.

Do I need to add the gable ends?

Yes, and this page does not do it for you. A gable is a triangle, so measure its width at the base and its height from the base to the peak, multiply the two and halve it, then add that to the wall area before you run the page — or run the page with the rectangle you have and add the gable separately. A house with two gables of 24 by 6 feet has 144 square feet of extra wall, which is another two squares and about 20 panels.

What else do I have to buy besides the siding?

Everything that finishes the edges, and all of it is bought by the linear foot rather than by area: J-channel for the soffit line and around every window and door, corner posts at every outside and inside corner, a starter strip along the bottom course, drip cap above the windows and doors, and the fascia and soffit if you are doing those at the same time. Count them from the elevation — one corner post per corner at the wall height, J-channel as the perimeter of every opening — rather than trying to derive them from the wall area.

Vinyl Siding Calculator

Result

Siding to buy (squares of 100 ft²)

Panels to buy: 123
Surface area in square feet: 930 ft²
Surface area in square metres: 86.40 m²

Vinyl siding calculator: enter the total length of the walls, the height to the eave and the area of the windows and doors, choose the panel you are buying and how much of each course shows, and it returns the squares and the number of panels to order. The square is the unit this trade quotes in — one square is 100 square feet of wall by definition — and the exposure is the number that catches people: it is how much of each course you actually see, not how wide the panel is. A panel sold as double 4 has two 4 inch laps rolled into it, so one panel covers 8 inches of wall, and the same panel laid as a single 4 covers half as much. That is why the exposure is a field: the same house with the same walls needs twice the siding at a 4 inch exposure as at 8. Two smaller things follow from the same arithmetic. The last panel in every course is cut, and a cut-off from one course rarely fits the next, so the panel count and the square count are rounded up separately and will not divide evenly into each other. And a gable end is a triangle, not a rectangle: measure its width and its height and take half, then add that to the wall area before you use this page.

Linear feet of siding per square, by exposure

Exposure	Linear feet per 100 ft²	Linear metres per 10 m²	Square feet per panel
Single 4 (4 in exposure)	300	98.43	4.17
Single 5 (5 in exposure)	240	78.74	5.21
Single 6 (6 in exposure)	200	65.62	6.25
Double 4 (8 in exposure)	150	49.21	8.33
Triple 3 (9 in exposure)	133.3	43.74	9.38

Choose the exposure first and read the row: the second and third columns tell you how much panel it takes to cover a fixed area, which is what the order is actually made of. The fourth column is for a 12 foot 6 inch panel, the most common length, and it is the number that turns linear feet into panels — divide your wall area by it and round up. The spread across the rows is the whole decision: 300 linear feet at a single 4 against 133 at a triple 3, for exactly the same wall. Nothing in this table is a manufacturer's figure for a particular product; it is the arithmetic of the exposure, which is why it holds for any panel of that profile.

Formula

Squares = ceil( ( length × eave height − openings ) × ( 1 + wastage ÷ 100 ) ÷ 100 )

L: Total length of the walls being sided, in feet
H: Height from the base to the eave line, in feet
A: Area of windows, doors and other openings, in square feet
p: Length of one panel, in feet
e: Exposure width — how much of each course shows, in inches
w: Wastage allowance as a percentage of the wall area

Use it once you have chosen the siding profile, because the exposure is a property of the panel rather than of the wall, and it is the input that moves the answer most. The exposure is written on the carton: double 4 means an 8 inch course, triple 3 means 9 inches, and a single 4 means 4. Measure the perimeter of the floor you are siding rather than guessing at a house width, and measure the eave height on the gable end too, because the wall area under the rake is the same rectangle whether or not the gable sits above it. Deduct the windows and doors, and then add the gable ends separately as width times height divided by two — a triangle is the one shape this page cannot take as an input, and forgetting it is the most common way a siding order comes up short. If you are siding a second storey over an existing wall, run the two floors separately and add: the band between them is trim, not siding, and it is bought by the foot.

Worked examples

A 120 foot perimeter, 9 foot eave, double 4 panels
1. Wall area: 120 × 9 = 1,080 square feet, less 150 square feet of windows, doors and the garage door = 930 square feet (86.4 m²)
2. With 10% wastage: 930 × 1.10 = 1,023 square feet
3. Squares: 1,023 ÷ 100 = 10.23, rounded up to 11 squares
4. One panel covers 12.5 × 8 ÷ 12 = 8.33 square feet: 1,023 ÷ 8.33 = 122.8, rounded up to 123 panels
These are the page defaults and a 30 by 30 foot single storey house. Note that 11 squares and 123 panels are not two ways of saying the same thing: 11 squares is 1,100 square feet and the panels add up to 1,025, because a square is a unit of wall and a panel is a unit of product. The gap between them is the off-cuts — every course ends in a cut panel, and the piece left over is usually too short to start the next course with.
A 100 foot garage wall with no openings, single 4 panels
1. Wall area: 100 × 8 = 800 square feet (74.32 m²), with no openings to deduct
2. With 10% wastage: 800 × 1.10 = 880 square feet
3. Squares: 880 ÷ 100 = 8.8, rounded up to 9 squares
4. One panel covers 12.5 × 4 ÷ 12 = 4.17 square feet: 880 ÷ 4.17 = 211.2, rounded up to 212 panels
The same square footage as a 100 by 8 wall in double 4 would be 106 panels — half the exposure means nearly twice the panels for the identical wall. The square count barely moves (9 against 9), which is exactly why the trade quotes in squares and buys in panels: the square is a property of the wall, and the panel count is a property of the profile you chose.
A 60 foot wall, 10 feet high, triple 3 panels, 100 ft² of openings
1. Wall area: 60 × 10 = 600 square feet, less 100 square feet of openings = 500 square feet (46.45 m²)
2. With 10% wastage: 500 × 1.10 = 550 square feet
3. Squares: 550 ÷ 100 = 5.5, rounded up to 6 squares
4. One panel covers 12.5 × 9 ÷ 12 = 9.375 square feet: 550 ÷ 9.375 = 58.67, rounded up to 59 panels
A wide exposure on a tall wall, which is the cheapest combination per square foot of wall: 59 panels to cover 500 square feet, against the 132 that single 4 would take. The trade-off is the look and the wind. A wide course reads as a bigger, flatter wall, and every lap is a place where wind can get behind the panel — which is why the exposure goes down as the design wind speed goes up, and why the panels are nailed loose in the slots rather than tight.

Limitations

The wall area and the panel coverage are exact; the wastage allowance is the estimate, and the openings are an assumption of their own. Ten percent is normal for a rectangular wall with the siding run horizontally, and it is not enough for a wall with a lot of corners, a garage door with a surround, or a house with several gables, because every one of those ends a course in a cut. The openings are deducted as flat areas, which is right for the glass but optimistic around the trim: a window with a wide surround has less siding around it than the rectangle suggests, and a door does not reduce the course count, only the length of the courses it interrupts. Gable ends are not counted at all, because a triangle is a different shape rather than a different number — measure the width and the height of each one and add width times height divided by two to the wall area. Nothing else on the job is in this arithmetic. J-channel, corner posts, starter strip, drip cap, soffit, fascia and the trim around every opening are all bought by the linear foot and none of them can be worked out from a wall area: they depend on how many corners, openings and eave lines the house has, so count them from the elevation instead. Housewrap, the tape for it and the nails are not counted either. Finally, this page does not check the wind: the exposure you can use, the nailing pattern and whether the wall needs sheathing behind the siding all come from the manufacturer's tables for your wind speed and your wall, not from a coverage calculation.

Frequently asked questions

How much siding do I need for a 1,200 square foot house?: About 11 squares for a single storey 30 by 30 house with a 9 foot eave and 150 square feet of openings: the walls are 1,080 square feet, less the openings is 930, and 10% wastage takes it to 1,023, which is 11 squares. The floor area of the house is not the number to use — a 1,200 square foot single storey and a 1,200 square foot two storey have very different wall areas, and only the wall area matters here.
What is a square of siding?: One hundred square feet of wall, and it is a definition rather than a package size — unlike a bundle of shingles or a box of flooring, a square of siding is always exactly 100 square feet whatever you buy. That is why this page does not treat siding as a coverage product with a range: there is nothing to vary. What does vary is how much product it takes to cover a square, and that is the exposure.
What is the exposure on vinyl siding?: Exposure width is how much of each course you see once the lap above it is in place — the vertical height one panel adds to the wall. A double 4 panel has two 4 inch laps formed into it, so it covers 8 inches; a triple 3 covers 9; a single 4 covers 4. The exposure is printed on the carton, and it is the single input that changes the order most: halving it nearly doubles the panels for the same wall.
Why do the squares and the panels not match up?: Because they measure different things and are rounded up separately. The square count is the wall area with wastage, divided by 100; the panel count is the same area divided by the area of one panel as it is actually laid. The panel count is the higher of the two in product terms because every course ends in a cut and the off-cut rarely fits the next course, so the panels you buy always cover a little more wall than the wall you have.
Do I need to add the gable ends?: Yes, and this page does not do it for you. A gable is a triangle, so measure its width at the base and its height from the base to the peak, multiply the two and halve it, then add that to the wall area before you run the page — or run the page with the rectangle you have and add the gable separately. A house with two gables of 24 by 6 feet has 144 square feet of extra wall, which is another two squares and about 20 panels.
What else do I have to buy besides the siding?: Everything that finishes the edges, and all of it is bought by the linear foot rather than by area: J-channel for the soffit line and around every window and door, corner posts at every outside and inside corner, a starter strip along the bottom course, drip cap above the windows and doors, and the fascia and soffit if you are doing those at the same time. Count them from the elevation — one corner post per corner at the wall height, J-channel as the perimeter of every opening — rather than trying to derive them from the wall area.

References

Approximate Conversions from U.S. Customary Measures to Metric — the chart behind feet, inches and square metres on this page — National Institute of Standards and Technology
The International System of Units (SI) brochure — the square metre the wall areas are converted to — Bureau International des Poids et Mesures (BIPM)

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