Siding Calculator - Squares, Panels, Trim & Cost

How to use it

1. Pick the input mode. Quick estimate takes a footprint (length by width), the number of stories, the wall height, and the roof style and pitch, then handles openings as a percentage allowance. Detailed takeoff lets you enter each wall, each gable, and each opening by hand when you have measured the house.
2. In quick mode, set the roof style. A gable roof adds two gable triangles sized from your pitch; a hip or flat roof adds none, because those walls stop at the plate.
3. Set the pitch when you have gables. The tool computes the gable rise as half the gable-end width times pitch over twelve, then draws the elevation so you can sanity-check it. Not sure of your pitch? Measure it with the roof pitch calculator and come back.
4. Choose the opening allowance in quick mode (12 percent is a sensible default), or in detailed mode add each door, window and garage door and choose whether to deduct them. Pros often leave small windows in to self-fund waste.
5. Choose the material. It sets the buy unit and a sensible default waste: vinyl by the box, fiber cement, engineered wood and cedar by the plank at your exposure, board and batten by the sheet plus battens, or metal by the panel at your coverage width.
6. Set the complexity so the waste is honest: 10 percent for a simple rectangle, 12 for an average elevation with some cuts and gables, 15 for a complex facade with many gables and dormers. The percentage stays editable.
7. Turn on the accessory takeoff and set your corner counts. Starter strip, J-channel, utility trim, corner posts, house wrap and fasteners all size themselves from the geometry you entered.
8. Read the takeoff: net area and squares up top, then the material count in real SKUs with the leftover shown, then every accessory line rounded up to whole pieces, rolls, posts and boxes.
9. Walk the cost ledger. Every unit price is editable, and labor and tear-off are optional per-square-foot rates you set from local quotes. The total is a planning number, not a bid.
10. Use the coverage reference table at the bottom to check plank counts by exposure, or print it for the supply counter.

At a glance

• One-story ranch, 40 x 30 footprint, 9 ft walls, gable 6/12, vinyl: 1,260 sq ft of wall plus 225 sq ft of gables, less a 12% opening allowance = 1,334 sq ft net; with 10% waste, 8 boxes of vinyl plus starter, J-channel, corners, 2 rolls of wrap and nails.
• Two-story colonial, 36 x 28, 8/12 gable, Hardie 8.25 in at 7 in exposure: 2,289 sq ft net, 2,518 with 10% waste; at 7 sq ft of coverage per 12 ft plank that is 360 planks, plus corners, J-channel and wrap.
• One 24 ft gable-end wall at 5/12, board and batten on 4 x 8 sheets: 276 sq ft net, 304 with 10% waste = 10 sheets, plus 25 battens on the wall running about 29 pieces of stock at 10 ft.

How the math works

Every number comes from a formula you can check by hand. Wall area: in quick mode the perimeter is 2 x (length + width), the wall height is your per-story height times the story count, and the gross wall area is perimeter times height. In detailed mode it is the sum of each wall's width times height. Gable area: each gable rise is half the gable-end width times pitch over twelve, and each gable triangle is 0.5 x width x rise; a gable roof has two gable ends, a hip or flat roof has none. Openings: in quick mode the allowance is your percentage of the gross wall area; in detailed mode each opening is width times height times count, and you choose whether to deduct all of them, none of them, or all but the small ones under a threshold (the pro convention). Net area is gross wall minus deducted openings plus gables. Squares are net area divided by 100, because a siding square is 100 sq ft. Waste-adjusted area is net times one plus the waste percentage. Vinyl: adjusted squares divided by 2 squares per box, rounded up; the leftover coverage is shown. Lap siding (fiber cement, engineered wood, cedar): coverage per plank is exposure in feet times plank length, and the count is adjusted area divided by that coverage, rounded up. Board and batten: sheets are adjusted area divided by sheet area, and battens per wall are the wall width in inches divided by the spacing, plus one, run out as linear feet and cut from your stock length. Metal: panels per wall are the wall width in inches divided by the coverage width, rounded up, full height, with a cut run added across each gable. Accessories: starter is the perimeter divided by 12 ft pieces; J-channel is the opening perimeters (plus gable rakes on vinyl) divided by 12.5 ft pieces; utility trim is the under-window widths plus the top-of-wall run; corner posts are your corner count times the wall height divided by a 10 ft post; house wrap is the gross wall plus gable area with a 10 percent overlap, divided by roll coverage; fasteners are about 2 lb of nails per square, or roughly 80 screws per square for metal. Cost is each count times an editable unit price, plus optional labor and tear-off at your per-square-foot rate times the net measured area.

1. 1. Build the gross wall area

   Siding covers walls, not floor area, so start from the wall rectangles. In quick mode the tool wraps the footprint: a 40 x 30 house has a 140 ft perimeter, and at a 9 ft wall height that is 140 x 9 = 1,260 sq ft of wall per story. Two stories doubles the height to 18 ft and the area to 2,520. In detailed mode you enter each wall's width and height and the tool sums them, which is the honest path for an L-shaped or split-level house where the footprint shortcut would miss returns and bump-outs.

2. 2. Add the gable triangles from the pitch

   A gable roof leaves a triangle of wall above the plate on each gable end, and it is easy to forget. The rise is half the gable-end width times the pitch over twelve: a 30 ft gable end at 6/12 rises 15 x 0.5 = 7.5 ft, so each triangle is 0.5 x 30 x 7.5 = 112.5 sq ft, and two ends add 225 sq ft. A hip roof has no gable triangles because every wall meets the eave, and a flat roof has none either. That is why the roof style matters here even though this is not a roofing tool.

3. 3. Deduct openings honestly

   Doors, windows and garage doors do not get sided, but small windows are often left in the count on purpose because their offcuts feed the waste. In quick mode a 12 percent allowance off the wall area is a good starting point. In detailed mode you enter each opening and pick the rule: deduct all of them, none of them, or all but the small ones under a threshold (the default 10 sq ft floor). A 40 x 30 ranch at a 12 percent allowance drops 151 sq ft, leaving 1,260 - 151 + 225 = 1,334 sq ft net.

4. 4. Add waste, then convert to real SKUs

   Divide net area by 100 to get squares (1,334 sq ft is 13.3 squares), then add waste for cuts and starts: 10 percent on a simple rectangle, 12 on an average elevation, 15 on a cut-up facade. Now the buy unit depends on the material. Vinyl ships two squares per box, so 13.3 squares at 10 percent (14.7) is ceil(14.7 / 2) = 8 boxes. Lap siding counts by exposure, not board width: an 8.25 in Hardie plank at 7 in exposure covers only 7 in of wall per course, so a 12 ft plank covers 7 sq ft, and you divide the adjusted area by 7. Board and batten counts sheets plus battens; metal counts full-height panels by coverage width.

5. 5. Take off the accessories and price the job

   The trim is what stalls a job when it runs short. Starter strip runs the whole perimeter, J-channel frames every opening (and the gable rakes on vinyl), utility trim caps the under-window sills and the top of the wall, and corner posts run the full wall height at each inside and outside corner. House wrap covers the gross wall plus gables with a 10 percent overlap. Then every count meets an editable price in the ledger, and you can add labor and tear-off as per-square-foot rates. The result is a planning total you control, which is exactly what you need to read a residing bid: compare its square count to yours first, then its line items.

Worked scenarios, start to finish

Real jobs with the numbers carried all the way through, so you can see how the estimate is built and check your own figures against them.

The judgement calls a pro makes

Decisions the tool cannot make for you, and how someone who does this for a living thinks them through.

Deduct every opening, or leave the small ones in

The trade convention is to deduct doors and garage doors but leave small windows in the square count, because a window's offcuts rarely feed another course and counting the wall as solid quietly funds part of your waste. On a plain elevation with a few windows, leaving them in and dropping the explicit waste a point or two nets out about the same. On a facade that is mostly glass, deduct everything and add waste on top, or you will badly over-order. The detailed mode's small-opening rule automates the common middle path; the threshold is yours to move.

Picking the waste band

Waste on siding runs lower than on roofing because most courses are straight runs, but a cut-up elevation still eats material at every gable rake, dormer and jog. Use 10 percent for a simple rectangle, 12 for an average house with a gable or two, and 15 for a complex facade with multiple gables, dormers and returns. Dutch lap and diagonal patterns lose more at the cuts, so nudge up a point. When in doubt on vinyl, round up: full boxes are usually returnable, while a mid-job top-up can arrive from a different production run with a visible color shift.

Ordering lap siding by exposure, not board width

This is the single most expensive siding mistake. A plank's nominal width is not what it covers: an 8.25 in Hardie plank laps the course below it and only exposes about 7 in to the weather, so it covers 7 sq ft over a 12 ft length, not 8.25. Order by the board width and you come up roughly one course short across the whole house. The exposure you choose also sets the look, so decide it first, then let the coverage math follow. The coverage table at the bottom of the page lists the common exposures and their real square-foot coverage.

Whether the old siding comes off

Vinyl can sometimes go over existing siding, and the tear-off line going to zero is tempting, but recladding over old material hides rot and failed flashing, telegraphs every old bump, and can trap moisture against the sheathing. Fiber cement and most modern systems want a clean, wrapped wall underneath and a fresh house wrap as the drainage plane. Budget the tear-off unless you have a specific reason to reclad in place, and always plan new house wrap on a full reside: it is cheap insurance behind a twenty-year cladding.

One color lot, ordered once

Vinyl and prefinished fiber cement vary slightly batch to batch, which is invisible in the box and obvious on a wall in raking light. Order the full count, waste allowance included, in one purchase from one lot, and have the supplier confirm the lot numbers match. This is the practical reason to trust the rounded-up box or plank count rather than buying tight and topping up: the top-up is the patch you will see from the street for the life of the siding.

Common mistakes, and the fix

• × Sizing siding from the house's floor area instead of the wall area.

  ✓ Floor area and wall area are unrelated: a compact two-story has far more wall per square foot of floor than a sprawling ranch. Always measure the walls, perimeter times height per story, and add the gables. This tool builds the wall area from the footprint or from your wall list, never from floor area.

• × Forgetting the gable triangles on a gable roof.

  ✓ Every gable end adds a triangle of wall above the plate, and on a steep roof it is real area: two 30 ft gables at 6/12 add 225 sq ft, more than a full square. Set the roof style and pitch so the tool adds them, and remember a hip roof adds none.

• × Ordering lap planks by board width instead of exposure.

  ✓ A plank covers only its exposure, the part that shows below the plank above it. An 8.25 in board at 7 in exposure covers 7 sq ft per 12 ft, not 8.25. Divide the wall area by the exposure coverage, which is what this tool does, or you will finish about a course short.

• × Skipping the trim takeoff and stalling mid-job.

  ✓ Starter strip, J-channel, utility trim and corner posts are separate SKUs, not offcuts of the field siding. Running out of J-channel with three walls done stops the job cold. Take off every accessory line up front; they are driven by the perimeter, the openings and the corners, not by area.

• × Buying tight and topping up later, mixing dye lots.

  ✓ A two-box top-up from a different production run can land a shade off and read as a band across the wall. Order the full waste-included count in one lot, keep the leftover for repairs, and return unopened boxes rather than under-ordering on purpose.

• × Treating the cost total as a contractor quote.

  ✓ The ledger prices materials at your editable numbers and lets you add rough labor and tear-off. It does not know your local labor market, flashing details, rot repairs, or disposal fees. Read it as a planning range to sanity-check a bid, never as the bid itself.

Material and unit specifics

The siding square

One square is 100 sq ft of wall, the same unit roofing uses. Quotes, coverage figures and labor rates are all quoted per square, so converting your wall area to squares first makes every other number line up. A 1,334 sq ft house is 13.3 squares of siding.

Vinyl by the box

Vinyl ships two squares to a box, so a box covers about 200 sq ft. Panels are roughly 12 ft 6 in long, and the profile (double 4, double 5, dutch lap) sets the exposure, which changes how many courses you run but not the box count. Vinyl is the lightest and cheapest system, forgiving for a DIYer, and it needs the full accessory kit: starter, J-channel, utility trim and corner posts are not optional.

Fiber cement and engineered wood lap

Fiber cement (the Hardie class) and engineered wood (the LP class) are counted by exposure. Fiber cement planks run 12 ft, engineered wood commonly 16 ft, and both expose about 7 in on an 8.25 in board. Fiber cement is heavy, needs carbide blades and a dust plan, and holds paint for decades; engineered wood is lighter and easier to cut but wants careful flashing and paint upkeep. Both want a proper drainage plane behind them.

Cedar bevel and other real wood

Cedar bevel siding is sized by exposure like fiber cement, with an 8 in bevel commonly run at about 6.5 in exposure. It is the priciest field material here and the most maintenance, but nothing matches its look and it takes stain or paint well. Because coverage per piece is low at typical exposures, the piece count runs high, so the coverage table is worth a look before ordering.

Board and batten

Board and batten is a vertical system: sheets or wide boards cover the field, and narrow battens cover the seams on a regular spacing, 12 in on center by default. It is counted as two lines, sheets by area and battens by spacing and run, and the battens over a gable are shorter on average because they climb the triangle. Note this tool treats board and batten only as an exterior siding material. For an interior accent wall, where the job is solving even batten spacing to the sixteenth and marking the wall, use the board and batten calculator instead.

Metal panels and house wrap

Metal panel siding is counted by coverage width, commonly 36 in, run full height, with a cut run added across each gable, and it fastens with screws rather than nails at roughly 80 per square. House wrap is the drainage and air barrier behind every system: it covers the gross wall plus gables with about a 10 percent overlap, and a 9 ft by 100 ft roll covers about 900 sq ft. Plan cap nails or fasteners and seam tape with it.

Reading your result

The squares figure is your wall in the trade's unit, and it is the first number to check against any bid: if a residing quote prices 18 squares and this page computes 13, ask about the gap before discussing anything else, because every material and labor line scales from it. The material count is a purchase order rounded up to whole boxes, planks, sheets or panels, and the leftover coverage note tells you how much spare the rounding bought, worth keeping for repairs or returning unopened in one lot. The accessory rows are separate purchases every professional order sheet carries, not padding: a job that runs out of corner posts or J-channel stops until the next supply run. Read the cost ledger as a materials floor at your edited prices; installed siding commonly runs a wide range per square foot depending on material, region, stories, tear-off and access, so treat any labor figure you add as a planning band, not a promise. A bid whose square count matches yours and whose line items you recognize is a bid worth negotiating; a bid far off either is a bid worth questioning.

Limitations

• Quick mode treats the house as a simple box with uniform walls and, on a gable roof, two matching gables. An L-shape, a split-level, dormers, or bump-outs need the detailed wall-by-wall mode or a real measurement.
• Soffit and fascia are measured and ordered separately and are not part of this takeoff. This tool sizes wall cladding, trim and wrap only.
• Waste bands are planning estimates. A very cut-up Victorian can exceed 15 percent, and a plain rectangle with a careful crew can beat 10.
• Prices are editable defaults, not live quotes. Local pricing, color-lot availability and delivery move the total, and the labor and tear-off rates are yours to set from real quotes.
• Imperial units only (feet, inches, square feet). There is no metric mode, consistent with the rest of the site.
• Pitch is used only to size and draw the gables. Measuring or solving a pitch, and any rafter or roof-area work, lives on the roof pitch and roofing calculators.
• Flashing, trim boards around windows and doors, soffit vents, and specialty pieces are real line items on a full order sheet and are not counted here.

Frequently asked questions

How many squares of siding do I need for a 1,500 sq ft house?

It depends on the wall area, not the floor area. A 1,500 sq ft single-story ranch is roughly a 50 x 30 footprint with about 160 ft of perimeter; at 9 ft walls that is about 1,440 sq ft of wall, plus gables. With a 6/12 gable roof adding around 170 sq ft and a 12 percent opening allowance, the net lands near 1,420 sq ft, or about 14 squares before waste, roughly 15.5 with 10 percent. A two-story 1,500 sq ft house has less footprint but more wall, often closer to 18 to 20 squares. Enter your own footprint and roof style for the real number.

How much does it cost to side a 1,500 sq ft house?

As a planning range: siding materials often land around $150 to $400 per square (100 sq ft) at retail once field siding, trim, corners, house wrap and fasteners are counted, so a roughly 16 square house is about $2,400 to $6,400 in materials depending on whether it is vinyl or fiber cement or cedar. Installed, siding commonly runs $4 to $12 or more per square foot of wall depending on material, region, stories, tear-off and access, which puts a full reside of this size in a wide band from around $8,000 to well over $20,000. This tool prices the materials line by line at prices you edit and lets you add labor and tear-off, so the total reflects your house and your local numbers, not a national average.

How much is a square of siding?

A square is 100 sq ft of wall. In materials, a square of vinyl is often around $150 to $250 once panels, trim and corners are included; fiber cement runs higher, roughly $250 to $550 a square in materials; cedar higher still. Installed, a square of siding commonly runs $400 to $1,200 or more depending on material, region and complexity. The per-square figure is useful for comparing quotes, but confirm what each quote includes, since some fold in tear-off, wrap and trim and others do not.

Do you subtract windows and doors when calculating siding?

Doors and garage doors, yes: they are large and you would over-order by counting them as solid wall. Small windows are usually left in the square count on purpose, because their offcuts rarely feed another course and counting the wall as solid quietly covers part of your waste. The common pro rule is to deduct openings larger than a threshold (around 10 sq ft) and leave the small ones in, which is exactly the default this calculator offers in detailed mode. On a facade that is mostly glass, deduct everything and add waste on top instead.