Roman Numerals
Convert numbers to and from Roman numerals
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How do Roman Numerals work?
Roman numerals are a number system from ancient Rome using combinations of letters: I, V, X, L, C, D, and M.
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
- Seven symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000
- Symbols are added left to right: VI = 5+1 = 6, XII = 10+1+1 = 12
- Subtractive notation: a smaller value before a larger one is subtracted: IV = 5−1 = 4, IX = 10−1 = 9
- Only I, X, and C can be subtracted, and only from their next two higher symbols: IV, IX, XL, XC, CD, CM
Where do Roman numerals come from?
It is thought Roman numerals come from hand signals and tally marks. The stroke I represents a finger, the V represents the gap between thumb and fingers for five, and the X represents hands crossed for ten. The L, C, D, and M come from modifications of Greek letters like chi, theta, and phi to represent 50, 100, 500, and 1,000. Over time, these marks changed into the Latin letters people recognize today. There is no 0 in the Roman alphabet, as the concept for the number 0 didn't fully develop until India invented it around 600 CE / 10600 HE.