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Roman Numerals Converter
This Roman numerals converter works both ways: type a number from 1 to 3999 and get its Roman numeral, or type a Roman numeral such as MMXXVI and get the number back. It checks your input as you type, so an invalid numeral or a number out of range gets a friendly explanation instead of a wrong answer. A reference table below the tool covers the symbols you will use most.
Roman numerals use the symbols I, V, X, L, C, D and M. The system has no zero and no symbol for numbers above 3999.
How it works
Roman numerals are built from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. Most numerals are made by adding symbols together from largest to smallest — so 2026 becomes MM (2000) + XX (20) + VI (6), which is MMXXVI. The one twist is subtractive notation: when a smaller symbol sits before a larger one, it is subtracted. That is why 4 is IV (5 minus 1) instead of IIII, and 9 is IX (10 minus 1) instead of VIIII.
To convert a number to Roman numerals, the tool works through the value pairs from largest to smallest — 1000 (M), 900 (CM), 500 (D), 400 (CD), 100 (C), 90 (XC), 50 (L), 40 (XL), 10 (X), 9 (IX), 5 (V), 4 (IV), and 1 (I) — appending each symbol as many times as it fits and subtracting its value, until nothing is left. To convert back, it reads the numeral left to right, adding each symbol's value, except when a smaller symbol comes before a larger one, in which case it subtracts instead.
The system only covers 1 to 3999, because the largest standard numeral is MMMCMXCIX (3999) and there is no symbol for zero — the Romans had no zero at all. Valid numerals follow strict rules: no symbol repeats more than three times in a row (so IIII is wrong), V, L, and D are never repeated, and subtraction is only allowed in the six pairs IV, IX, XL, XC, CD, and CM. The converter checks all of this. If you type something like IC or VV, it will tell you the numeral is not valid rather than guessing a number.
| Number | Roman | Number | Roman |
|---|---|---|---|
| 1 | I | 50 | L |
| 5 | V | 100 | C |
| 10 | X | 500 | D |
| 9 | IX | 1000 | M |
| 4 | IV | 3999 | MMMCMXCIX |
Worked example
Suppose you want the year 2026 written in Roman numerals, as you might see on a building or a movie credit. Here is how the converter works it out.
Step 1: Leave the direction on Number → Roman and type 2026.
Step 2: The converter takes the largest value first: 1000 fits twice, so it writes MM and 26 is left.
Step 3: 10 fits twice, so it writes XX and 6 is left.
Step 4: 5 fits once, so it writes V and 1 is left, then 1 fits once, so it writes I.
The tool gives exactly this result: MMXXVI — 2026 in Roman numerals. In the other direction, typing XLII gives 42: XL is 40 and II is 2.
FAQ
How do you convert a number to Roman numerals?
Break the number into thousands, hundreds, tens, and ones, then write each part with Roman symbols from largest to smallest. For example, 2026 is 2000 (MM) + 20 (XX) + 6 (VI), giving MMXXVI. Use the subtractive pairs IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900) where they fit. This converter does the same steps automatically.
What is the largest number in Roman numerals?
The largest standard Roman numeral is 3999, written MMMCMXCIX. The system has no symbol for 5000 or for zero, so numbers above 3999 cannot be written in the classical form. If you type 4000 or more into this converter, it will ask for a number between 1 and 3999.
Why is 4 written as IV and not IIII?
Roman numerals use subtractive notation: a smaller symbol placed before a larger one is subtracted from it. IV means 5 minus 1, which is 4. Writing IIII was sometimes seen on old clocks, but it is not standard — the same rule gives IX for 9, XL for 40, XC for 90, CD for 400, and CM for 900.
Is there a Roman numeral for zero?
No. The Romans had no symbol for zero and no place-value system, so zero simply does not exist in Roman numerals. The smallest Roman numeral is I, for 1. That is one reason the system was replaced by the numbers we use today, which handle zero and large values far more easily.
How do I read a Roman numeral like MCMLXXXIV?
Read it left to right, adding each symbol's value, and subtract when a smaller symbol comes before a larger one. MCMLXXXIV is M (1000) + CM (900) + L (50) + XXX (30) + IV (4), which totals 1984. Type any numeral into the Roman → Number mode on this page and the converter will show the same breakdown.