Roman Numeral Converter
100% private — runs on your device, never uploaded. Works offline once loaded.
Convert any whole number from 1 to 3999 into Roman numerals, or translate a Roman numeral back into a number — instantly as you type. Malformed numerals are validated and rejected. Everything runs in your browser.
How Roman numerals work
Roman numerals combine seven letters — I (1), V (5), X (10), L (50), C (100), D (500) and M (1000) — using addition and subtraction. Symbols are written largest-first and added together (so LXVI is 50 + 10 + 5 + 1 = 66). When a smaller symbol sits before a larger one it is subtracted, which is how IV becomes 4 and CM becomes 900.
Subtraction follows strict rules: only I, X and C can be subtracted, each only from the next two higher symbols (I before V or X, X before L or C, C before D or M). That's why 99 is XCIX, not the tempting-but-invalid IC. This converter enforces those rules by building the canonical numeral and rejecting anything that doesn't match.
Why the limit is 3999
Standard Roman numerals stop at 3999 (MMMCMXCIX) because there is no basic letter for 5000 or 10000. Larger values historically used an overline (a vinculum) to multiply a numeral by 1000, but that notation isn't part of everyday usage and isn't universally supported in plain text, so this tool sticks to the classic 1–3999 range.
Where you'll still see Roman numerals
They persist in more places than you'd expect, which is why a quick converter stays useful.
- Movie and game sequels, and copyright years in film credits
- Super Bowl numbering and other sporting events
- Clock and watch faces, building cornerstones and monuments
- Book chapters, outline headings and preliminary page numbers
- Monarch and pope names — Elizabeth II, Louis XIV
Reading and writing them accurately
To turn a number into a numeral, work through the place values from thousands down, subtracting the largest chunk you can each time — 1994 becomes M (1000) + CM (900) + XC (90) + IV (4) = MCMXCIV. To read a numeral, scan left to right and add each symbol, subtracting any symbol that is smaller than the one to its right. This converter does both directions live and validates the result, so you can trust the output rather than double-checking by hand.
Frequently asked questions
What is the largest number I can convert?
3999, written MMMCMXCIX. Standard Roman numerals have no symbol for 5000 or higher, so values above 3999 fall outside the everyday system this tool supports.
Why is 4 written IV and not IIII?
Standard notation limits any symbol to three repeats and uses subtraction instead, so 4 is IV (one before five). You'll occasionally see IIII on clock faces as a stylistic choice, but it isn't the standard form, and this converter treats it as invalid.
Can Roman numerals represent zero or negatives?
No. The Roman system has no symbol for zero and no concept of negative numbers, which is one reason it was eventually replaced by the Hindu-Arabic numerals we use for arithmetic today.
How do I convert a year like 2026?
Choose number-to-Roman mode and type 2026 to get MMXXVI (1000 + 1000 + 10 + 10 + 5 + 1). The tool updates instantly as you type and you can copy the result with one click.
Why does my Roman numeral get rejected?
The converter validates by rebuilding the canonical numeral and comparing. If your entry uses illegal repeats (IIII), invalid subtractions (VX, IC) or non-numeral letters, it won't match a valid number and is rejected so you never get a wrong answer.
Is anything uploaded when I convert?
No. Conversion runs entirely in your browser using a small lookup table, so whatever you type never leaves your device.
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