Look up paper size dimensions in mm and inches
Type a paper name and get its exact size in millimetres and inches: A4 is 210 by 297 mm, Letter is 8.5 by 11 inches. Works for A4, A3, Letter, Legal and Tabloid, always in portrait. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Size
- A4
- Width mm
- 210
- Height mm
- 297
- Width in
- 8.2677
- Height in
- 11.6929
Paper names are convenient until a document, printer, layout, or shipping workflow needs exact measurements. This paper size lookup turns five widely used names—A4, A3, Letter, Legal, and Tabloid—into their portrait width and height in both millimetres and inches. Enter one supported name and receive a small structured result ready for display, validation, or application code. Matching is case-insensitive and tolerates surrounding spaces, while an unknown name produces a clear input error instead of a guessed dimension. The lookup is deterministic, uses a fixed table, makes no network request, and always returns the same values for the same recognized size.
Choose the paper name that matches the real document
Start with the label used by the printer, document template, or physical stock: A4, A3, Letter, Legal, or Tabloid. A4 is the familiar general office format in countries that use the ISO A series, while A3 doubles an A4 sheet’s area and is commonly chosen for diagrams, posters, and spreads. Letter is the everyday North American office format.
Legal is longer than Letter and is often associated with contracts or forms that need additional vertical space. Tabloid is the eleven-by-seventeen-inch format used for newsletters, posters, drawings, and large tables. Send that name in the size field.
Capitalization does not matter, and surrounding whitespace is removed, so values such as a4, A4, and a padded Letter label resolve consistently. The accepted vocabulary is intentionally limited. Names such as Ledger, A5, Executive, or a custom measurement are rejected because silently treating a nearby format as equivalent could cause clipping, scaling, wasted stock, or an incorrect page box.
A successful response repeats the canonical display name, making it straightforward to store clean metadata even when the original input used inconsistent capitalization. This narrow contract keeps validation predictable for forms and automated integrations.
Read width and height in millimetres and inches
Measurements are reported in portrait orientation, meaning the width is the shorter edge and the height is the longer edge. A4 returns 210 by 297 millimetres, and A3 returns 297 by 420 millimetres. Letter returns 215.9 by 279.4 millimetres and 8.5 by 11 inches.
Legal keeps the Letter width but extends the height to 355.6 millimetres or 14 inches. Tabloid returns 279.4 by 431.8 millimetres or 11 by 17 inches. The North American sizes originate from exact inch measurements, with corresponding millimetre values based on 25.4 millimetres per inch.
If your application needs landscape orientation, swap width and height after the lookup rather than requesting a different name. Keeping the stored answer in portrait order makes comparisons reliable and prevents orientation from being confused with paper stock. These values describe the physical sheet or page box, not a printer’s printable area.
Hardware margins, bleed, trim, and safe zones depend on the printer and production process, so account for them separately when placing content.
Use strict errors to protect layouts and print workflows
Missing values, empty strings, arrays, and other non-string values are also rejected. This behavior is useful in production because a paper size typo should stop a job before a PDF is generated, a print order is submitted, or a template is selected. Handle the error beside the size field in an interactive form, or log it with the source record in a batch import so an operator can correct the data.
Do not replace an error with a default unless your product has an explicit documented default; assuming Letter for an unknown international document, or A4 for an unknown North American form, can change pagination and crop content. In a document service, use the returned millimetres for metric layout engines and the returned inches for print settings expressed in imperial units. In inventory or procurement software, store the canonical name alongside dimensions so people can search by the familiar label while machines compare numeric values.
The algorithm performs only normalization, validation, and a constant-time table lookup. It does not access the network, infer a likely size, read a file, resize content, or mutate a document. That separation keeps the result explainable: recognized input produces exact published dimensions, and everything else produces a correction-ready error.
What you can do with it
Configure document page boxes
Translate a supported paper label into numeric dimensions before creating a PDF, report, or print stylesheet.
Validate print order metadata
Reject misspelled or unsupported stock names before a job reaches layout, procurement, or production.
Normalize product and template records
Store a canonical paper name with millimetre and inch dimensions across mixed metric and imperial systems.
FAQ
Which paper sizes are recognized?
The lookup recognizes exactly A4, A3, Letter, Legal, and Tabloid. Matching is case-insensitive and surrounding spaces are ignored.
Are the measurements portrait or landscape?
They are portrait dimensions, with the shorter edge returned as width. Swap width and height in your application for landscape use.
Why are ISO inch values rounded?
ISO A sizes are defined here by their standard integer millimetre dimensions. Their inch equivalents are rounded to four decimal places for stable, readable output.
What size is Letter paper in millimetres?
Letter measures 215.9 by 279.4 millimetres, which is exactly 8.5 by 11 inches. The millimetre values come from the inch sizes at 25.4 millimetres per inch, so they are exact rather than rounded.
What is the difference between Letter and Legal paper?
Both are 8.5 inches wide, but Legal is longer: 14 inches, or 355.6 millimetres, against 11 inches for Letter. Legal is often chosen for contracts and forms that need extra vertical space.
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/misc2/paper-size-lookup \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"size":"A4"}'const res = await fetch("https://api.kit.forhosting.com/misc2/paper-size-lookup", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"size": "A4"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/misc2/paper-size-lookup",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"size": "A4"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/misc2/paper-size-lookup", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"size":"A4"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"size":"A4"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/misc2/paper-size-lookup", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"size": "A4"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "misc2.paper_size_lookup",
"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
Choose the paper name that matches the real document
If your source data contains aliases, normalize those aliases to one of the five supported names before calling the lookup.
Read width and height in millimetres and inches
Every successful result contains five fields: the canonical size name, width_mm, height_mm, width_in, and height_in. The API price is $0.002 for each successful item.
Use strict errors to protect layouts and print workflows
An unrecognized name returns an invalid_input error with a message that lists the five supported choices.
Technical questions
What happens when the size name is unknown?
The request fails with an invalid_input error that identifies the unrecognized value and lists the supported choices. No nearby size is guessed.
How much does an API lookup cost?
Each successful API item costs $0.002. The browser implementation uses the same deterministic lookup logic.