Roman numerals still appear on clock faces, book chapters, movie copyright lines, Super Bowl logos, monarchs’ names and building cornerstones. Reading them is a matter of knowing seven letters and one subtraction rule, but writing larger numbers correctly and spotting invalid forms is where most people stumble. This converter works in both directions, validates every numeral against the standard rules, and goes beyond 3,999 using the vinculum, the bar that multiplies a numeral by a thousand.
How to use the Roman numeral converter
- Choose the direction: Number → Roman or Roman → Number.
- Enter a whole number from 1 to 3,999,999, or type a numeral. Lowercase letters are fine.
- For values of 4,000 and up, type the thousands with an overline (V̅) or in parentheses — (IV)CCXX means 4,220.
- The tape shows the result, a copyable text version, and the parentheses form. The steps and tables break the number down place by place. Malformed numerals produce a message explaining what is wrong.
The rules of Roman numerals
There are seven symbols:
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1,000 |
Standard notation follows four rules:
- Symbols are written from largest to smallest, left to right, and added: XVI = 10 + 5 + 1 = 16.
- A smaller symbol before a larger one is subtracted, but only in six pairs: IV, IX, XL, XC, CD, CM.
- I, X, C and M may repeat up to three times in a row; V, L and D never repeat.
- A bar over a numeral multiplies it by 1,000.
Every number from 1 to 3,999,999 has exactly one standard form under these rules, so the converter checks your numeral by computing its value and comparing it with the standard spelling of that value.
Worked example: 1994
Split into place values: 1,000 + 900 + 90 + 4
1,000 → M; 900 → CM; 90 → XC; 4 → IV
Result: MCMXCIV
Reading it back, pair each smaller symbol with the larger one after it: M (1,000), CM (900), XC (90), IV (4), for a total of 1,994.
A large example: 12,345 is 12 thousands plus 345. Twelve is XII, so the thousands are written X̅I̅I̅, and 345 is CCCXLV, giving X̅I̅I̅CCCXLV, or (XII)CCCXLV in plain text.
Roman numerals chart
| Number | Numeral | Number | Numeral | Number | Numeral |
|---|---|---|---|---|---|
| 1 | I | 11 | XI | 40 | XL |
| 2 | II | 12 | XII | 50 | L |
| 3 | III | 14 | XIV | 90 | XC |
| 4 | IV | 15 | XV | 100 | C |
| 5 | V | 19 | XIX | 400 | CD |
| 6 | VI | 20 | XX | 500 | D |
| 7 | VII | 24 | XXIV | 900 | CM |
| 8 | VIII | 29 | XXIX | 1,000 | M |
| 9 | IX | 30 | XXX | 5,000 | V̅ |
| 10 | X | 39 | XXXIX | 1,000,000 | M̅ |
Readable but not standard
Some forms appear in real life even though they break the rules. Clock faces commonly show IIII for 4, and inscriptions sometimes use IIX for 8 or XIIX for 18. This converter applies the standard rules strictly to ordinary numerals, so IIII, IIX and IC are rejected with an explanation of the problem. It is more lenient with the vinculum, where conventions vary: V̅MM for 7,000 is accepted, and the standard form (V̅I̅I̅) is shown alongside.
Where you will see them
Roman numerals mark the year of production in film and TV credits, the edition of the Super Bowl and the Olympics, regnal numbers (Elizabeth II, Louis XIV), outline levels and front-matter page numbers in books, and the hours on traditional clocks. For arithmetic with numerals, use the Roman numeral calculator; for birthdays, anniversaries and tattoo designs, the Roman numeral date converter formats a full date.
Frequently asked questions
How do you write 2026 in Roman numerals?
MMXXVI. Break the number into place values — 2,000 + 20 + 6 — and write each one: MM + XX + VI.
Why is 4 written IV and not IIII?
Standard notation uses subtraction to avoid four repeated symbols: a smaller numeral placed before a larger one is subtracted. Only six pairs are allowed: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Clock faces often show IIII by tradition, but it is not standard.
How do you write numbers larger than 3,999?
Draw a horizontal bar, called a vinculum, over a numeral to multiply it by 1,000. V̅ is 5,000, X̅ is 10,000 and M̅ is 1,000,000. Typed text often uses parentheses instead: (V) = 5,000. That is how this converter reaches 3,999,999.
Is there a Roman numeral for zero?
No. The Roman system had no zero or negative numbers. Medieval writers sometimes used N, for nulla (nothing), in tables, but it never became part of the numeral system.
What makes a Roman numeral invalid?
Common errors are repeating I, X, C or M more than three times (IIII), repeating V, L or D at all (VV), and using a subtraction pair that is not allowed, such as IC for 99 (correct: XCIX) or VX for 5 (correct: V).