Roman numerals
Type a whole number from 1 to 3999 and get its standard Roman numeral: 1994 becomes MCMXCIV and 3999 becomes MMMCMXCIX, ready for a title page, an outline or an engraving. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- N
- 2,024
- Result
- MMXXIV
- Roman
- MMXXIV
Standard Roman numerals encode whole numbers with seven letters: I, V, X, L, C, D, and M. This converter takes a single integer from 1 to 3999 inclusive and returns the canonical subtractive spelling used in modern style guides, copyright lines, outline numbering, and exam papers. Enter 4 and you receive IV, not IIII; enter 1994 and you receive MCMXCIV; enter 3999 and you receive MMMCMXCIX, the largest value the classic alphabet can write without overlines.
What Roman numerals are and how this converter spells them
Standard Roman numerals use seven letters whose values never change: I is one, V is five, X is ten, L is fifty, C is one hundred, D is five hundred, and M is one thousand. Modern printed style writes numbers by combining those letters from largest to smallest, with six subtractive pairs that prevent four identical letters in a row: IV for four, IX for nine, XL for forty, XC for ninety, CD for four hundred, and CM for nine hundred.
This converter implements that convention with a thirteen-entry table walked greedily: while the remaining value is at least the next weight, the matching letters are appended and the weight is subtracted. The result is always the unique shortest canonical spelling, so 4 becomes IV rather than IIII, 9 becomes IX rather than VIIII, 44 becomes XLIV, 1990 becomes MCMXC, and 2024 becomes MMXXIV. There is no letter for zero, no negative numerals, and no fraction glyphs here; those need other notations.
Classic letters without a vinculum overline stop at 3999, written MMMCMXCIX, which is why the accepted integer range is closed at one through 3999.
Where integer-to-Roman conversion is used, and what this tool will not do
Publishers still set copyright years in Roman numerals on title pages, colophons, and film credits, which is why a year such as 2026 should become MMXXVI without a one-off spreadsheet. Legal and academic outlines number major sections I, II, III and mix Arabic and Roman markers in subsections; generating those labels from a loop of integers avoids off-by-one typos when a chapter is inserted. Clockmakers, monument inscriptions, and exam papers also need a single canonical spelling so graders and engravers do not argue about IIII versus IV.
This capability is deliberately one-way: it does not parse a Roman string back to Arabic, it does not emit vinculum overlines for values at or above 4000, and it does not encode uncia twelfths or other fractional Roman units. If you need those, use a dedicated large-numeral or fraction converter rather than stretching this range. Keep n inside the published limits and you get a stable string you can stamp into PDF credits, CMS widgets, and homework oracles without standing up a typesetting library of your own.
What you can do with it
Copyright years and film credits
Render a publication or production year as a Roman numeral (for example 2026 to MMXXVI) for title pages, colophons, and closing credits.
Outline and clause numbering
Generate I, II, III section markers from a loop of integers so legal briefs, syllabi, and table-of-contents builders stay in canonical subtractive form.
FAQ
What range of integers can I convert to Roman numerals?
Whole numbers from 1 to 3999 inclusive. There is no standard letter for zero, and 3999 (MMMCMXCIX) is the largest value classic symbols can write without a vinculum overline.
Why does 4 become IV instead of IIII?
Modern subtractive notation writes four as IV (one before five) rather than four I letters. Additive clock-face IIII is a typographic tradition this converter does not emit.
Can I convert a Roman string back to an Arabic integer?
No. This landing is integer to Roman only.
How do I write 2026 in Roman numerals?
2026 is MMXXVI: two M for two thousand, XX for twenty and VI for six. Type the year and the converter returns it, ready for a title page, a colophon or film credits.
What value does each Roman letter have?
I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Their values never change; only the order decides whether a letter adds or subtracts.
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/conv/roman-numerals \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"n":2024}'const res = await fetch("https://api.kit.forhosting.com/conv/roman-numerals", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"n": 2024
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/roman-numerals",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"n": 2024
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/roman-numerals", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"n":2024}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"n":2024}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/roman-numerals", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"n": 2024
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.roman_numerals",
"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
min | 1 |
max | 3999 |
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
Zero, negatives, fractions, and integers outside that closed range fail with invalid_input and are not billed.
What Roman numerals are and how this converter spells them
Additive clock faces that print IIII for four are a typographic tradition, not the subtractive form this endpoint returns.
Input contract, range checks, and the JSON you get back
After coercion the solver checks that n is a whole number inside the inclusive interval from 1 to 3999. On success the body echoes n as a number, sets roman and result to the same uppercase letter string, and leaves optional keys omitted rather than null. Example: n equals 2024 yields roman MMXXIV; n equals 4 yields IV; n equals 3999 yields MMMCMXCIX. Pair this with your own display code if you need lowercase letters or interpuncts; the contract is always the canonical uppercase string. POST a JSON object with one required integer field named n. Aliases value, number, and integer are accepted so forms and SDKs can use a name that already exists in the payload. The value may arrive as a JSON integer or as a digit string with an optional leading plus sign; fractions, scientific notation, empty strings, arrays, and non-numeric text such as a Roman string itself are rejected. Zero is not a Roman numeral in this alphabet, 4000 would require a vinculum or an extra M beyond the classic four-M cap, and negatives have no standard letters, so those cases raise invalid_input naming field n and are not billed. The published price is $0.002 per successful API call.
Where integer-to-Roman conversion is used, and what this tool will not do
Because the algorithm is a short table walk with no network and no model tokens, every successful request stays at the parse-tier price $0.002 and failed validation does not consume prepaid balance.
Integration use cases
Homework and style-guide checks
Let students and copy editors confirm that 4 is IV, 9 is IX, and 1994 is MCMXCIV against the same greedy table the API uses.
Technical questions
What happens if I send 0, 4000, or a decimal?
The task fails with invalid_input. n must be an integer from 1 to 3999; fractions, zero, negatives, and values above 3999 are out of range and are not billed.
What does the Roman numerals converter cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.