How Roman numerals work
Seven letters stand for values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Values are added from largest to smallest (MDCLXVI = 1666), except that a smaller numeral before a larger one is subtracted, but only in six standard pairs: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
So 1994 is M + CM + XC + IV = MCMXCIV. The converter uses these rules strictly, which means it rejects non-standard forms like IIII, IC or VX with a clear message rather than guessing.
Big numbers and dates
Standard numerals stop at 3,999 (MMMCMXCIX). For larger values, a line over a numeral multiplies it by 1,000 (the vinculum): V̅ = 5,000. The converter writes and reads these up to 3,999,999.
Dates (popular for tattoos, wedding engravings and anniversary gifts) are converted part by part: 24.10.2025 → XXIV.X.MMXXV. Choose the separator you want, and double-check the order (day–month or month–day) before anything is engraved.
Auto mode
In auto mode each line is detected separately: numbers become numerals, numerals become numbers, and dates are converted part by part.
Worked example
Here is what the Roman Numeral Converter returns for its built-in example. Settings used: Convert: Auto (both ways); Date separator: Dot; Lowercase (iv): off. Click Try an example in the tool above to load it, then change it as you like.
2025
MCMXCIV
14
4999
IIIIMMXXV
1994
XIV
I̅V̅CMXCIX
⚠ IIII: “IIII” is not a valid Roman numeral.Questions
What is 2025 in Roman numerals?
MMXXV: MM (2000) + XX (20) + V (5).
Is IIII a valid Roman numeral?
Not in standard notation; 4 is IV. IIII does appear on some clock faces by tradition.
How do you write 5,000 in Roman numerals?
With a vinculum (overline): V̅. Standard numerals without overlines only go up to 3,999.
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