Math
Roman Numerals Converter
Convert any number from 1 to 3,999 into a Roman numeral, or paste a numeral like MCMXCIV and get 1,994 back, with validation that catches malformed input instead of guessing. Roman numerals still show up everywhere numbers need a formal look: Super Bowl editions, movie copyright years, book chapters, clock faces and tattoo dates. The awkward part is the subtractive notation, where IV means 4 but VI means 6, and this tool both applies those rules and shows you the breakdown so the answer is checkable rather than a black box. Everything runs in your browser with nothing sent to a server.
Convert
standard subtractive notation
Standard modern notation, 1 to 3,999. Numerals are validated, so IL and IIII are rejected rather than guessed at.
How the Roman numerals converter works
Going from a number to a numeral is a greedy subtraction: the tool walks a value table from 1,000 down to 1, and at each step writes the symbol as many times as it fits. The table includes the six subtractive pairs as first-class entries, which is the whole trick; with CM worth 900 in the table, 1,994 naturally becomes M then CM then XC then IV without any special cases.
Value table
M 1000 · CM 900 · D 500 · CD 400 · C 100 · XC 90 · L 50 · XL 40 · X 10 · IX 9 · V 5 · IV 4 · I 1reading a numeral: add each symbol, but subtract it when the next symbol is larger
Notes & assumptions
- Range is 1 to 3,999, the limit of standard plain-text notation.
- Input numerals are validated against the repeat and subtraction rules; lowercase is accepted and uppercased.
- Nonstandard historical forms such as IIII are rejected, matching what schools and style guides expect.
Symbols, subtractive pairs and years
Three small tables cover nearly every lookup people actually need: the seven symbols, the six legal subtractive pairs, and the years that show up in copyrights and anniversaries.
| Symbol | Value | Subtractive pair | Value | Year | Numeral |
|---|---|---|---|---|---|
| I | 1 | IV | 4 | 1969 | MCMLXIX |
| V | 5 | IX | 9 | 1990 | MCMXC |
| X | 10 | XL | 40 | 1994 | MCMXCIV |
| L | 50 | XC | 90 | 2000 | MM |
| C | 100 | CD | 400 | 2024 | MMXXIV |
| D | 500 | CM | 900 | 2026 | MMXXVI |
| M | 1000 | 3999 | MMMCMXCIX |
Notice that every subtractive pair uses only I, X or C as the subtractor, and each subtracts only from the next two steps up its own ladder. That is why 49 is XLIX (40 + 9) and never IL, and why 1,666, which uses every symbol exactly once in descending order, comes out as the tidy MDCLXVI.
Worked example
Convert 1,994 by walking the value table. M fits once (1,994 − 1,000 = 994). CM fits (994 − 900 = 94). D, CD and C do not fit. XC fits (94 − 90 = 4). Then IV closes it out (4 − 4 = 0). Written in order: MCMXCIV. Reading it back confirms the answer: 1,000 + 900 + 90 + 4 = 1,994.
Now this year: 2,026 takes M twice (2,026 − 2,000 = 26), skips everything down to X, which fits twice (26 − 20 = 6), then V and I once each. Result: MMXXVI. The same walk explains why numerals get long around the 8s and 9s of each digit: 1,888 is MDCCCLXXXVIII, thirteen characters, while the larger 2,000 is just MM.
Frequently asked questions
How do Roman numerals work?
Seven letters carry fixed values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. You add the values reading left to right, except when a smaller symbol sits before a larger one, which subtracts it: IV is 4, IX is 9. So MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1 = 2026.
What is 2026 in Roman numerals?
2026 is MMXXVI: two M for 2,000, two X for 20, then VI for 6. Nearby years: 2024 is MMXXIV, 2025 is MMXXV, and 2030 will be MMXXX.
Why is 4 written IV and not IIII?
Standard modern notation uses subtractive pairs to keep numerals short: IV for 4, IX for 9, XL for 40, XC for 90, CD for 400 and CM for 900. The Romans themselves were inconsistent, and IIII survives on many clock faces to this day. This converter follows the standard subtractive form, which is what schools and style guides expect.
What is the largest number in Roman numerals?
With the seven basic symbols and the rule of at most three repeats, the largest standard numeral is MMMCMXCIX, which is 3,999. Larger numbers historically used a bar over a symbol to multiply it by 1,000, but that vinculum notation is not representable in plain text, so this tool stops at 3,999.
Is there a Roman numeral for zero?
No. The system counts things and has no symbol for nothing; medieval scribes sometimes wrote the word nulla instead. That is why this converter starts at 1, and why Roman numerals never developed place value the way decimal digits did.
How do I read a long numeral like MCMXCIV?
Scan it in chunks, watching for a smaller value before a larger one. MCMXCIV splits into M (1,000), CM (900), XC (90) and IV (4), which totals 1,994. If a symbol is followed by something bigger, the pair subtracts; otherwise it adds. The converter shows this breakdown for any numeral you paste in.
What are the rules for valid Roman numerals?
I, X, C and M may repeat up to three times in a row; V, L and D never repeat. Only I, X and C can subtract, and only from the next two values up: I before V or X, X before L or C, C before D or M. That makes IL for 49 invalid (correct is XLIX) and IIII nonstandard for 4. The converter flags input that breaks these rules.