Roman Numeral Converter
Type a number or a Roman numeral — the converter works out which way to go, explains every place value, spots invalid numerals and tells you why. Then try the 10-question quiz.
Roman numerals use seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Write them largest to smallest and add, or put a smaller letter first to subtract — only IV, IX, XL, XC, CD and CM are allowed. So 1947 = M + CM + XL + VII = MCMXLVII.
Number or numeral
Number → RomanDigits convert to Roman; letters I V X L C D M convert to a number.
A bar on top multiplies by 1,000. You can also type a barred group in brackets: (IV)CCC = 4,300.
Place-by-place breakdown
The seven symbols & memory tricks
| Symbol | Value | Memory trick |
|---|---|---|
| I | 1 | One straight stick — like a single tally mark. |
| V | 5 | Spread one hand: the gap between thumb and fingers makes a V for five fingers. |
| X | 10 | Two Vs meeting at their points — 5 + 5. |
| L | 50 | Half of C. Picture an L-shaped half-century stand. |
| C | 100 | Latin centum — as in century and cent (100 paise or cents). |
| D | 500 | Began as the right half of an old 1,000 sign — so it is half of M. |
| M | 1,000 | Latin mille — a millennium is 1,000 years, a millimetre is 1/1,000 m. |
Remember the order from smallest to largest:
The rules a valid numeral follows
- Write symbols from largest to smallest and add them: XVI = 10 + 5 + 1 = 16.
- I, X, C and M can repeat, but at most three times in a row: III = 3, but 4 is IV, not IIII.
- V, L and D are never repeated (VV would just be X).
- A smaller symbol before a larger one is subtracted — only six pairs are allowed: IV, IX, XL, XC, CD, CM.
- V, L and D are never subtracted, and only one symbol may be subtracted at a time (IIX ✗).
- A bar (vinculum) on top multiplies by 1,000: V̅ = 5,000, X̅ = 10,000. There is no symbol for zero.
Roman numerals around you — right now
Clock faces, book chapters, movie sequels, monarchs and building foundation stones still use Roman numerals.
Roman numeral quiz — 10 questions
Pick a direction and a number range.
| # | Question | Your answer | Correct answer |
|---|
Read and write Roman numerals with confidence
Roman numerals use seven letters and two simple ideas — add when a symbol is the same or smaller than the one before, subtract when a smaller symbol comes first.
Type anything
A number like 1947 or a numeral like MCMXLVII — the direction is detected for you.
Read the breakdown
See each place value (thousands, hundreds, tens, units) turned into symbols.
Fix mistakes
Invalid numerals like IIII, VV or IC are flagged with the exact rule they break.
Take the quiz
10 questions, both directions, with a review of every answer at the end.
Number → Roman
Split the number by place value and convert each part: 1947 = 1000 + 900 + 40 + 7 = M + CM + XL + VII = MCMXLVII.
Roman → Number
Go left to right. If a symbol is smaller than the next one, subtract it; otherwise add it. MCMXC = 1000 + (1000 − 100) + (100 − 10) = 1990.
Common mistakes
99 is XCIX, not IC. 49 is XLIX, not IL. 45 is XLV, not VL. 4,000 is I̅V̅, not MMMM.
Where you see them
Clock faces, chapter and lesson numbers, class names (Class X), sequels and kings (Louis XIV), and the year on old buildings.
Roman Numeral Converter — your questions
What are the rules for writing Roman numerals?
Write symbols from largest to smallest and add them, so XVI = 16. I, X, C and M may repeat up to three times in a row, but V, L and D are never repeated. A smaller symbol placed before a larger one is subtracted, and only six such pairs are allowed: IV, IX, XL, XC, CD and CM.
How do I write 49 and 99 in Roman numerals?
49 is XLIX and 99 is XCIX. Convert place by place: 49 is 40 + 9 = XL + IX, and 99 is 90 + 9 = XC + IX. IL and IC are wrong, because I can only be subtracted from V or X, and only one symbol may be subtracted at a time. The same logic makes 45 equal XLV, not VL.
How do I convert a Roman numeral back to a number?
Read left to right. If a symbol is smaller than the one after it, subtract it; otherwise add it. For MCMXC: M is 1000, then CM is 1000 − 100 = 900, then XC is 100 − 10 = 90, giving 1990. Working in place-value chunks like this is quicker and safer than adding letter by letter.
Is there a Roman numeral for zero?
No. The Roman system has no symbol for zero and no place value, which is why arithmetic was so awkward with it. Zero came into use through the Indian number system, where Brahmagupta set out rules for it, and it is the reason the Hindu-Arabic digits we use today replaced Roman numerals for calculation.
How do you write numbers above 3,999 in Roman numerals?
A bar on top, called a vinculum, multiplies the symbol by 1,000: V̅ is 5,000 and X̅ is 10,000. So 4,000 is I̅V̅, not MMMM, because M cannot repeat four times. This converter accepts barred symbols from the keypad and also lets you type a barred group in brackets, so (IV)CCC means 4,300.
Why do some clocks show 4 as IIII instead of IV?
The IIII on a clock face is called the clockmaker's four. It balances the VIII directly opposite it, and it made casting easier because the same mould could produce the I, V and X symbols in regular batches. Both forms are seen on real clocks, and this tool has a tick box to switch between them.