Conversion · General Conversion
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Roman Numeral Converter
Switch direction to convert a number (1–3999) to a Roman numeral, or a Roman numeral back to a number, using standard subtractive notation.
Direction
Roman numeral
MCMXCIV
1994
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Standard subtractive notation
Roman numerals build a number from the symbols I (1), V (5), X (10), L (50), C (100), D (500) and M (1000), read left to right and normally added together. When a smaller symbol appears immediately before a larger one, it's subtracted instead — IV means 5 − 1 = 4, IX means 10 − 1 = 9 — which is how the system avoids ever repeating a symbol more than three times in a row.
The symbols
I=1 · V=5 · X=10 · L=50 · C=100 · D=500 · M=1000
Worked example
1994 = 1000 (M) + 900 (CM) + 90 (XC) + 4 (IV) = MCMXCIV.
Frequently asked questions
Why is there no Roman numeral for zero?
The Roman numeral system was built for counting and record-keeping, and it never developed a symbol for 'nothing' the way Hindu-Arabic numerals later did with 0 — the concept of zero as a number in its own right wasn't part of the system at all, so there's no standard way to write it in Roman numerals.
Why does this calculator stop at 3999?
Standard Roman numerals use M (1000) as the largest symbol, and 3999 (MMMCMXCIX) is the largest number writable with three M's plus the standard subtractive combinations. Numbers of 4000 and above need an extended notation — a bar (vinculum) over a symbol to multiply it by 1000 — that isn't part of the everyday system this calculator covers.
Why is 'IIII' not accepted for 4?
Standard modern usage writes 4 with the subtractive form 'IV' (one less than five), not by repeating 'I' four times. 'IIII' does appear historically — most famously on some clock faces — but it isn't the canonical form this calculator produces or accepts as input.
Sources and method
- Standard Roman numeral subtractive notation — general published mathematics and history of numeral systems.