Siding calculator
A 1400 sq ft elevation with 200 sq ft of windows and doors leaves 1200 to clad: 12 squares, or 60 panels that cover 20 sq ft each. Enter the coverage printed on your carton. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Wall area
- 1,400
- Openings
- 200
- Panel coverage
- 20
- Net area
- 1,200
- Square area
- 100
- Squares exact
- 12
- Squares needed
- 12
Siding take-offs for vinyl, fiber-cement, and engineered-wood cladding start from a simple covering identity: net wall area after openings, divided by how much face each panel actually covers. This siding calculator accepts the gross wall area, the combined area of windows, doors, and other openings to deduct, and the coverage of one panel, then returns the net area, the number of siding squares, and the integer panel count you should order. One square is one hundred square units of face, typically one hundred square feet in North American practice.
How siding squares and panel count are computed from wall area
Gross wall area is the sum of the rectangular elevations you intend to clad, measured in one square unit. Panel count is a different packing of the same net face. Each manufactured plank covers a published exposure: length along the wall times the height that remains visible after the lap.
A fourteen-hundred square-foot elevation with two hundred square feet of openings and twenty square feet of coverage per panel has a net of twelve hundred, twelve exact squares, and sixty panels. A leftover of a few square feet still buys a whole extra plank because you cannot purchase a fraction of a board. The identity does not add a waste percentage, does not convert feet to metres, and does not assume a vinyl double-four profile: you pass the coverage printed on the carton you will hang.
All three inputs must be finite numbers.
Where a siding panel calculator earns its keep
Siding crews and exterior contractors estimate vinyl, fiber-cement, or engineered-wood planks before they leave the yard so they can close a house wrap instead of guessing from the last elevation. Homeowners recladding a garage, a gable, or a ranch need a panel count that matches the public calculator when they stand in the aisle with a tape and a window schedule.
Estimators and quantity-survey trainers pin goldens: fourteen hundred of wall with two hundred of openings at twenty of coverage per panel must stay sixty panels and twelve squares, and a leftover net that is not a whole number of panels must ceiling rather than truncate. Curriculum authors can show why deducting openings changes the order relative to a naive wall-area-only guess, which is the difference between a take-off and a wasteful overbuy.
If you later need drywall boards with screws, metal roofing panels, plywood sheathing, or a paint-litre estimate, treat those as separate search intents rather than overloading this siding landing. The tool is a covering take-off, not a substitute for a starter-strip schedule, a J-channel lineal, a corner-post count, or a waste factor your crew adds for rakes and gables. Failed validation is not billed, which keeps exploratory scripts cheap when you deliberately send openings larger than the wall to verify error handling.
Round-trip checks are easy: subtract openings from wall area by hand, divide by coverage per panel, ceiling to a whole plank, and confirm the published panels match.
What you can do with it
Order vinyl or fiber-cement siding for a house wrap
Enter gross wall area, the window and door schedule as openings, and the coverage printed on the carton to get an integer panel count before you load the trailer.
Gable, garage, and ranch reclad take-offs
Turn a rectangular elevation minus its openings into a siding order that matches the public calculator and the estimating pipeline, including the square count suppliers still quote.
Classroom covering checks on siding squares
Instructors and LMS auto-graders verify that fourteen hundred of wall with two hundred of openings at twenty of coverage yields sixty panels and twelve squares, not a guessed pallet.
FAQ
How do I calculate how many siding panels I need?
A 1400 ft² wall with 200 ft² of openings and 20 ft² per panel is 60 panels.
What is a siding square?
One siding square is 100 square units of net face. In North American practice the unit is square feet, so one square is 100 ft².
Should I use square feet or square metres?
Squares match supplier language when that unit is square feet. Mixing metres of wall with feet of panel coverage without converting will produce a wrong count.
What happens if the openings are larger than the wall?
The calculation stops instead of returning a negative order. Openings can be zero for a blank wall, but they can never exceed the wall area you entered.
Does the panel count include waste, trim or corner posts?
No. It covers only the net face: no waste percentage, starter strip, J-channel or corner posts are added. Count those separately and add the margin your crew usually leaves.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/build/siding \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"wall_area":1400,"openings":200,"panel_coverage":20}'const res = await fetch("https://api.kit.forhosting.com/build/siding", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"wall_area": 1400,
"openings": 200,
"panel_coverage": 20
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/build/siding",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"wall_area": 1400,
"openings": 200,
"panel_coverage": 20
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/build/siding", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"wall_area":1400,"openings":200,"panel_coverage":20}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"wall_area":1400,"openings":200,"panel_coverage":20}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/build/siding", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"wall_area": 1400,
"openings": 200,
"panel_coverage": 20
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "build.siding",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000 |
min_pos | 1e-15 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
When deducted openings exceed the total wall area the task fails with invalid_input instead of inventing a negative order.
How siding squares and panel count are computed from wall area
From that total you subtract openings: windows, doors, garage doors, and any other face that will not receive a plank. The remainder is net_area. A siding square is an industry lot of one hundred square units of that net face; when you work in square feet, one square is one hundred square feet, the same lot roofers use for shingles. squares_exact is net_area divided by one hundred, and squares_needed is that ratio rounded up so a leftover strip still consumes a full square on a supplier ticket that sells by the square. That product is panel_coverage. panels_exact is net_area divided by panel_coverage, and panels is the smallest integer greater than or equal to that ratio: ceil of net_area over panel_coverage. Openings may be zero when the elevation is blank; they may not exceed wall_area.
What you send, which units to use, and how validation fails
Use one consistent square unit for all three fields. A common vinyl plank twelve feet six inches long with an eight-inch exposure covers about eight point three three square feet; a fiber-cement lap with twelve-foot length and seven-and-a-quarter-inch exposure covers a different figure, which you read from the manufacturer, not from this page. Mixing square metres of wall with square feet of panel coverage without converting will overstate or understate the order by an order of magnitude, so the contract keeps one unit set and leaves conversion to the caller. Each field is capped at one billion in absolute magnitude so intermediate products stay finite. Send three required numeric fields. wall_area is a finite positive number for the gross exterior face; aliases area, walls, wall, and total_area are accepted so a take-off form does not need a rename. openings is a finite non-negative number for the combined hole area; aliases opening_area, deduct, windows_doors, and openings_area are recognized. panel_coverage is a finite positive number for the face one panel covers after the published exposure; aliases coverage, coverage_per_panel, panel_area, and panel_cover are accepted. Strings that parse as finite numbers are accepted the same as JSON numbers. On success the response echoes the cleaned inputs, publishes net_area, square_area as one hundred, squares_exact and squares_needed, panels_exact and the integer panels buy count, coverage_from_panels as panels times panel_coverage, spare_area as the leftover face those panels buy beyond the net, and formula as the covering identity. When openings exceed the total wall area the task fails with invalid_input and a message that names that condition; failed tasks do not consume prepaid balance. Successful API calls use the published base of $0.002 per item.
Technical questions
What happens if openings exceed the total wall area?
The task fails with invalid_input. Deducted openings cannot be larger than wall_area; a negative net face is a measuring error, not a materials list, and is not billed.
What does the siding calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.