Roman Numeral
—
Breakdown
Common References — click to load
About this tool
Roman Numeral Converter
Roman Numeral Converter goes both ways between numbers and Roman numerals, handling values from 1 up to 3,999,999.
How to use it
- Enter a number to convert to Roman numerals.
- Or enter Roman numerals to get the number.
- Copy whichever result you need.
The subtractive rule
The seven symbols are I=1, V=5, X=10, L=50, C=100, D=500 and M=1000. Ordinarily values are written largest first and added together, so MMXXIV builds up from 1000+1000+10+10+(5-1).
The subtractive rule is the exception: a smaller symbol before a larger one is subtracted, giving IV for 4 and IX for 9 rather than IIII and VIIII. Only six subtractive pairs are valid (IV, IX, XL, XC, CD, CM), which is why IL is not a legal way to write 49. It is XLIX.
Worked example
Reading a year:
- MMXXIVM+M+X+X+IV
- Arithmetic1000+1000+10+10+4
Result: 2024. The IV at the end is the subtractive pair, not a mistake.
When it helps
- Reading a copyright date or a cornerstone inscription.
- Numbering chapters, appendices or outline sections.
- Converting a clock face or a monarch's regnal number.
- Checking a numeral before engraving or printing it.
Common mistakes
- Inventing subtractive pairs. Only six are valid, so 99 is XCIX and never IC.
- Repeating a symbol more than three times. IIII appears on some clock faces by convention but is not standard notation.
- Expecting a zero. Roman numerals have no symbol for zero and no way to express one.
