Roman Numeral Converter
Convert numbers to Roman numerals and back, with breakdown and error checks
| Place | Value | Roman | How |
|---|---|---|---|
| Thousands | 2,000 | MM | M + M = 1,000 + 1,000 |
| Tens | 20 | XX | X + X = 10 + 10 |
| Ones | 6 | VI | V + I = 5 + 1 |
2,000 + 20 + 6 = 2,026
MM + XX + VI = MMXXVI
Pick a date to see it in Roman numerals.
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1,000 |
- I, X, C and M can repeat up to 3 times (III = 3, XXX = 30). V, L and D never repeat.
- A smaller symbol before a larger one is subtracted, only in six pairs: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
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Results are for general guidance. Please check anything important before relying on it. Terms of use
How to Use
- Type a number from 1 to 3,999 in the Number box to get its Roman numeral.
- Or type a Roman numeral (capital or small letters) in the Roman numeral box to get its value. The other box updates as you type.
- The breakdown table below shows each place value (thousands, hundreds, tens, ones), its Roman part and how that part is formed.
- If a numeral isn't valid, such as IIII or VX, the tool tells you which rule it breaks and gives the correct form.
- To write a date in Roman numerals, pick it under Date in Roman numerals and choose a separator. You get both the day-first and month-first forms, each with a copy button.
Roman numerals, explained place by place
Roman numerals are still used for class names (Class XII), book chapters and volumes, exam question parts (i, ii, iii), clock faces, page numbers in a preface, and years on monuments and film credits. This Roman numeral converter turns numbers from 1 to 3,999 into Roman numerals and back. It shows how each part is built, and if a numeral is invalid, it tells you why.
The seven symbols
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1,000 |
The rules
- Repeating adds: III = 3, XX = 20, CCC = 300. I, X, C and M can be repeated, but not more than three times in a row.
- V, L and D are never repeated. VV would just be X.
- Smaller after larger adds: VI = 5 + 1 = 6, LX = 60, MC = 1,100.
- Smaller before larger subtracts, but only in six pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. I goes only before V and X, X only before L and C, C only before D and M. V, L and D are never subtracted.
To convert a number, split it by place value and convert each part on its own:
= M + CM + XC + IV = MCMXCIV
Useful examples
| Number | Roman | Number | Roman |
|---|---|---|---|
| 4 | IV | 99 | XCIX |
| 9 | IX | 400 | CD |
| 12 | XII | 1947 | MCMXLVII |
| 40 | XL | 1950 | MCML |
| 49 | XLIX | 2026 | MMXXVI |
| 90 | XC | 3999 | MMMCMXCIX |
Common mistakes
- IC for 99 is wrong: I can only be subtracted from V and X. 99 = 90 + 9 = XCIX.
- VX for 5 is wrong: V is never written before a larger symbol. 5 is just V.
- IIII for 4 breaks the three-in-a-row rule, so write IV. Plenty of clock faces show IIII out of old habit, but IV is the standard form.
- IL for 49 is wrong: 49 = 40 + 9 = XLIX.
Zero and numbers above 3,999
The Roman system has no symbol for zero, and no way to write negative numbers or fractions in this form. With the standard symbols the largest number is 3,999 (MMMCMXCIX), because M can’t be repeated four times. For bigger numbers, a bar called a vinculum was drawn over a numeral to multiply it by 1,000: V̄ = 5,000, X̄ = 10,000 and M̄ = 10,00,000 (one million). Books don't agree on the details, so the tool shows the bar form for 4,000 to 39,99,999 as a guide but keeps the main converter to 1–3,999.