Roman Numeral Converter Pro
Convert between numbers and Roman numerals from 1 to 3,999,999 in both directions, batch-convert a pasted list or a numeric range, and see exactly why a malformed numeral is malformed. Everything runs in your browser.
MCMXCIV · plain: MCMXCIVA bar over a numeral multiplies it by 1,000 (vinculum). Classical Latin stops at 3,999 (MMMCMXCIX); anything from 4,000 up is the mediaeval/modern overline extension. Copyable plain text writes the bar as parentheses: (IV) = 4,000, ((D)) = 500,000.
Additive / subtractive breakdown
Greedy build order: at each step the largest unit that still fits is taken, and the six subtractive pairs are taken as a unit.
| # | Symbol | Role | Value | Running total |
|---|---|---|---|---|
| 1 | M | additive | +1,000 | 1,000 |
| 2 | C | additive | +100 | 1,900 |
| 3 | M | additive | +1,000 | 1,900 |
| 4 | X | additive | +10 | 1,990 |
| 5 | C | additive | +100 | 1,990 |
| 6 | I | additive | +1 | 1,994 |
| 7 | V | additive | +5 | 1,994 |
MCMXCIV = 2,216 = 1,994
Additive symbols total 2,216; 0 subtractive pair(s) remove 0. 7 symbols in total.
Batch conversion: pasted list and/or numeric range
Separate values with commas, spaces or new lines. A token shaped like 40-50 expands as an inclusive range. The start/end/step range is always added to the list, duplicates are collapsed, results are sorted and capped at 2,000 rows.
Quiz mode
Both directions, typed and multiple-choice, plus malformed numerals to spot. Every answer comes with the rule behind it.
Only the rules and the common-values table below are printed — no controls.
Roman numeral rules & common values
Symbol values
I= 1 ·V= 5 ·X= 10L= 50 ·C= 100 ·D= 500 ·M= 1,000- I, X, C, M are the repeatable "ten" symbols; V, L, D are the "five" symbols and never repeat.
The six subtractive pairs
IV= 4 ·IX= 9 ·XL= 40XC= 90 ·CD= 400 ·CM= 900- Those are the only legal subtractions — V, L and D are never subtracted.
Repetition & ordering
- I, X, C, M repeat at most three times: III, XXX, CCC, MMM.
- No VV, LL or DD, and never IIII, XXXX, CCCC or MMMM.
- Symbols run largest first; a smaller symbol before a larger one subtracts.
- A subtractive pair is used once, and never followed by a symbol ≥ the minuend.
Overline (vinculum) rules
- Classical Latin stops at 3,999 =
MMMCMXCIX. - One bar multiplies by 1,000, so V with a bar is 5,000.
- Copyable plain text uses parentheses:
(IV)= 4,000 ·(M)= 1,000,000. - Two bars (double parentheses) multiply by 1,000,000.
Common values
| Number | Roman (overline) | Plain text | Symbols |
|---|---|---|---|
| 1 | I | I | 1 |
| 2 | II | II | 2 |
| 3 | III | III | 3 |
| 4 | IV | IV | 2 |
| 5 | V | V | 1 |
| 6 | VI | VI | 2 |
| 7 | VII | VII | 3 |
| 8 | VIII | VIII | 4 |
| 9 | IX | IX | 2 |
| 10 | X | X | 1 |
| 11 | XI | XI | 2 |
| 12 | XII | XII | 3 |
| 13 | XIII | XIII | 4 |
| 14 | XIV | XIV | 3 |
| 15 | XV | XV | 2 |
| 16 | XVI | XVI | 3 |
| 17 | XVII | XVII | 4 |
| 18 | XVIII | XVIII | 5 |
| 19 | XIX | XIX | 3 |
| 20 | XX | XX | 2 |
| 30 | XXX | XXX | 3 |
| 40 | XL | XL | 2 |
| 50 | L | L | 1 |
| 60 | LX | LX | 2 |
| 70 | LXX | LXX | 3 |
| 80 | LXXX | LXXX | 4 |
| 90 | XC | XC | 2 |
| 100 | C | C | 1 |
| 200 | CC | CC | 2 |
| 300 | CCC | CCC | 3 |
| 400 | CD | CD | 2 |
| 500 | D | D | 1 |
| 600 | DC | DC | 2 |
| 700 | DCC | DCC | 3 |
| 800 | DCCC | DCCC | 4 |
| 900 | CM | CM | 2 |
| 1,000 | M | M | 1 |
| 1,969 | MCMLXIX | MCMLXIX | 7 |
| 2,024 | MMXXIV | MMXXIV | 6 |
| 3,999 | MMMCMXCIX | MMMCMXCIX | 9 |
| 4,000 | MMMM | MMMM | 4 |
| 1,000,000 | M() | 1 |
About this tool
This converter translates in both directions between whole numbers and Roman numerals from 1 to 3,999,999, batch-converts a pasted list or a numeric range, and explains every malformed numeral by naming the rule it breaks and quoting the offending symbols. It also shows the additive/subtractive breakdown of any numeral, a printable rules-and-values reference chart, and a scored quiz.
Everything runs in your browser: no value is uploaded, no request leaves the page, and the CSV export is built locally from a Blob. Batch input is capped at 2,000 rows and values at 3,999,999 so the tab stays responsive.
- 100% free — no account needed
- Runs in your browser
- Nothing is uploaded
Frequently asked questions
Is Roman Numeral Converter Pro really free?
Yes. Roman Numeral Converter Pro is completely free on PureBrowser — every feature, with no account, no trial, and no credit card.
Does Roman Numeral Converter Pro upload my data?
No. Roman Numeral Converter Pro runs entirely inside your browser, so anything you type, paste, or open stays on your own device.
Do I need to sign up or install anything?
Neither. There is no account and nothing to download — open the page and Roman Numeral Converter Pro is ready to use on desktop or mobile.
Does Roman Numeral Converter Pro work offline?
Once the page has loaded, yes. All of the processing happens locally in your browser, so it keeps working without a connection.
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