Square footage calculator
A 12 by 10 ft bedroom is 120 sq ft of floor, and with 10% waste you order 132 sq ft. Square yards appear alongside for carpet quotes, so one measurement serves flooring, tile and vinyl. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Length
- 12
- Width
- 10
- Waste percent
- 10
- Square footage
- 120 sqft
- Square yards
- 13.3333
- Waste factor
- 1.1
- Area with waste
- 132
This square footage calculator multiplies the length and width of a rectangular room or surface in feet to produce the exact floor or surface area in square feet, the unit most US finish suppliers and DIY stores use when you order flooring, carpet, underlayment, tile boxes, or vinyl. An optional waste percent expands the measured area into an orderable figure so cuts, pattern matching, and overage are not forgotten at checkout. The engine also reports square yards (divide by nine) because many carpet and broadloom products are still priced or rolled by the yard. Everything is pure finite arithmetic: no network calls, no random sampling, and no timestamps.
What your square footage means when you order flooring
Square footage is the planar area of a rectangle measured in feet on both sides: length times width equals square feet. For a 12 by 10 foot bedroom that is one hundred twenty square feet of floor; for a 20 by 15 patio that is three hundred square feet of surface. Finish materials are almost always sold against that number or against a waste-inflated copy of it.
Carpet stores often convert to square yards by dividing by nine because roll goods and labor tables still speak in yards; tile and laminate packages quote coverage in square feet and expect you to add five to fifteen percent for cuts and breaks. If you already need tile counts, paint litres, or sod rolls from a known area, use those dedicated tools after this page has given you a stable square-footage number.
Where square footage fits in remodeling, retail, and software workflows
Homeowners meet square-footage math when a flooring aisle asks how many square feet of LVP to buy, when a carpet estimator converts the room to yards before quoting, or when a tile calculator wants the open floor figure before box counts. Contractors use the same numbers to write room-by-room takeoffs, to compare supplier quotes that mix feet and yards, and to check that a junior estimator did not forget waste on a diagonal-laid pattern.
Teachers and vocational programs can generate answer keys for modest room dimensions without trusting opaque apps that silently switch units or round differently between runs. Developers call the same contract from scripts to seed deterministic test vectors for estimating tools, to normalize user-entered room sizes before a materials pipeline, or to satisfy programming-challenge statements that demand square footage rather than a hand-waved sketch.
Product and education tools use the formula when a learner types length and width in feet and the UI must show raw area, waste-adjusted area, and yards side by side.
What you can do with it
Flooring and carpet takeoffs
Convert room length and width in feet into square feet and square yards, then add waste before ordering boxes, rolls, or broadloom.
FAQ
What does the square footage calculator cost?
It is free in your browser on this page.
How is square footage calculated?
For a rectangular room or surface, square footage = length × width when both dimensions are in feet. Square yards = square footage ÷ 9.
Can I enter dimensions in metres?
Not directly. Convert to feet first (1 m ≈ 3.28084 ft), then enter length and width. The product is always treated as square feet.
Does this calculator return tile counts or paint litres?
No. It returns square footage and waste-adjusted area only. Use dedicated floor-tile, laminate, carpet, or paint tools after you have the area.
How do I convert square feet to square yards for carpet?
Divide the square footage by nine, which the tool does for you: 120 sq ft is 13.3333 sq yd. Many carpet and broadloom products are still priced or rolled by the yard, so both figures are shown, with and without waste.
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/home/square-footage \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"length":12,"width":10}'const res = await fetch("https://api.kit.forhosting.com/home/square-footage", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"length": 12,
"width": 10
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/home/square-footage",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"length": 12,
"width": 10
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/home/square-footage", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"length":12,"width":10}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"length":12,"width":10}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/home/square-footage", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"length": 12,
"width": 10
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "home.square_footage",
"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.
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
What square footage means for finish materials and what the response returns
This calculator returns the normalized length and width you entered, the raw square_footage product, the equivalent square_yards, the waste_percent and waste_factor you chose, the area_with_waste and yards_with_waste orderable figures, a unit tag of sqft, the precision used for rounding, a method tag length_times_width_feet, and a short formula string. There is no material catalog, no SKU list, and no shipping quote: the engine either multiplies finite positive dimensions inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing length or width, zero or negative dimensions, non-finite values, magnitudes above the documented ceiling, and waste outside the closed interval from zero to one hundred percent.
How length, width, and waste are read and how results stay reproducible
Optional leading plus signs and scientific notation on numeric strings are accepted when they parse as finite decimals; embedded spaces, currency symbols, and non-numeric tokens fail with a clear message so a bad paste does not become a wrong material order. Waste must sit between zero and one hundred inclusive: negative waste would shrink the order below the measured floor, and more than one hundred percent would more than double the order without an explicit multi-room workflow. The preferred fields are length and width in feet, with aliases l, room_length, len, and length_ft for length, and w, room_width, breadth, and width_ft for width so spreadsheets, query strings, and typed forms can reuse the same contract without renaming cells. Optional waste_percent defaults to zero when omitted so a pure geometry check stays exact; aliases waste, overage, and overage_percent map common estimator labels onto the same field. Both dimensions must be strictly positive; zero or negative sizes fail with invalid_input because they do not describe a physical room or surface. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for all numeric fields, defaulting to four and capped at fifteen so JSON goldens and UI snapshots stay stable across runtimes.
Where square footage fits in remodeling, retail, and software workflows
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a weekend remodel demo to an automated quote pipeline without changing the mathematical result. Pair it with floor-tile, laminate, carpet, or paint tools when you need material quantities after the area is known, and with other home endpoints when you are building a small lab of free, deterministic room calculators for finish takeoffs.
Integration use cases
Contractor room-by-room quotes
Produce reproducible square_footage and area_with_waste figures for each room when writing bids and comparing supplier units.
Deterministic estimate fixtures
Generate stable square-footage values for unit tests, teaching demos, and CI assertions on L×W geometry in feet.
Technical questions
What is waste_percent for?
Optional overage for cuts, pattern match, and install scrap. area_with_waste = square_footage × (1 + waste_percent/100). Defaults to 0 for exact area only.