Roman Numeral Converter
Convert a number into Roman numerals or read a Roman numeral back as a number. Both directions work in the same box — type digits to get numerals, or type numerals to get the value — covering 1 to 3,999,999 with the overline (vinculum) notation for thousands.
For numbers over 3,999, an overline multiplies a numeral by 1,000. To type one, put an underscore before it — for example _V is 5,000, or [V] also works.
How Roman numerals work
Roman numerals build every value from seven letters. Reading left to right, you add a symbol’s value when it is the same as or smaller than the one before it, and subtract it when a smaller symbol sits directly in front of a larger one. That subtractive trick is why 4 is IV rather than IIII and 90 is XC rather than LXXXX. No symbol repeats more than three times, and V, L, and D never repeat at all. Once numbers pass 3,999 — the largest you can write with plain letters — a bar drawn over a numeral (the vinculum) multiplies it by a thousand.
How it’s calculated
To convert a number, the tool greedily subtracts the largest fitting value from the list 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 and appends the matching symbols (M, CM, D, CD, C, XC, L, XL, X, IX, V, IV, I). For values above 3,999 it splits off the thousands, converts them the same way, and draws them with an overline. To read a numeral, it scans right to left, adding each symbol’s value unless it is smaller than the symbol to its right, in which case it subtracts — then multiplies any overlined section by 1,000.
Follows the common modern (subtractive, vinculum) convention. Historical inscriptions sometimes used additive forms like IIII, which this tool normalizes.
Symbol chart
| Symbol | Value | With overline |
|---|---|---|
| I | 1 | 1,000 |
| V | 5 | 5,000 |
| X | 10 | 10,000 |
| L | 50 | 50,000 |
| C | 100 | 100,000 |
| D | 500 | 500,000 |
| M | 1,000 | 1,000,000 |
Subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
Worked example
Take 2026. Break it into place values: 2000 + 20 + 6. That is MM (two thousands) + XX (two tens) + VI (five plus one), giving MMXXVI. Reading it back, M+M = 2000, X+X = 20, V+I = 6, total 2026. For a larger value like 5,000 — too big for plain letters — you write V with a bar over it, entered here as _V.
Common mistakes
- Writing four of a symbol in a row (IIII, XXXX) instead of using subtractive form (IV, XL).
- Repeating V, L, or D — these never double up.
- Subtracting the wrong pair: I only goes before V or X; X only before L, C, or M.
- Expecting a zero — Roman numerals have no symbol for it.
Where it is used
- Clock and watch faces, book chapters, and outline numbering.
- Movie copyright years and building cornerstones.
- Naming sequels, monarchs, and events like the Super Bowl and the Olympics.
- Learning place value and the history of number systems.
Frequently asked questions
What are the seven Roman numerals?
The seven symbols are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. Every Roman numeral is built by combining these, adding when a smaller symbol follows a larger one and subtracting when it precedes a larger one.
How do you write numbers over 3,999 in Roman numerals?
Because M (1000) is the largest symbol and no symbol repeats more than three times, values above 3,999 use a vinculum — an overline that multiplies a numeral by 1,000. So V with a bar is 5,000 and X with a bar is 10,000. This converter shows the bar and lets you type an underscore before a numeral (like _V) to enter it.
Why is 4 written IV and not IIII?
Roman numerals use subtractive notation to avoid four identical symbols in a row. Placing a smaller numeral before a larger one subtracts it, so IV = 5 − 1 = 4 and IX = 10 − 1 = 9. The same rule gives XL = 40, XC = 90, CD = 400, and CM = 900.
Is there a Roman numeral for zero?
No. The Roman system has no symbol for zero and no way to represent negative numbers or fractions of one in the standard scheme. It was designed for counting and tallying, so the smallest value it expresses is I (1).
What is the largest number this converter handles?
Using the vinculum (overline) method, the largest value is 3,999,999. Beyond that there is no widely agreed notation, so the tool caps the range at 1 through 3,999,999.