Roman Numeral to Number Converter
Convert Roman numerals to integers
Type a value above — result appears instantly
Roman Numeral to Number Converter
Paste a numeral from a clock face, a film's copyright line or a chapter heading and see the number. Each letter is marked as added or subtracted, and an invalid numeral gets a plain explanation of the rule it broke. Overlined numerals past MMMCMXCIX work too.
MCMXCIV becomes 1994. Tap a piece to see why.
CM is 1000 − 100, so it adds 900.
How to decode a Roman numeral
Enter the numeral
Upper or lower case both work. Add commas to decode several at once.
Read the number
The value shows as you type. If the numeral is not valid, like IIII or VX, you see which rule it breaks instead of a wrong answer.
Follow the parse
Every letter is marked as added or subtracted, with the running total beside it.
Copy or share
Copy the number or grab a link. Handy for double-checking a tattoo date or a homework answer.
How to read a numeral by hand
Go left to right. If a letter is smaller than the one after it, subtract it. Otherwise add it. That single comparison covers every valid numeral, so there is no table to memorise.
The rule
for each letter, next in numeral:if value(letter) < value(next):total -= value(letter)else:total += value(letter)return total| Letter | Value | Next | Action | Total |
|---|---|---|---|---|
| M | 1000 | C | + add | 1000 |
| C | 100 | M | − subtract | 900 |
| M | 1000 | X | + add | 1900 |
| X | 10 | C | − subtract | 1890 |
| C | 100 | I | + add | 1990 |
| I | 1 | V | − subtract | 1989 |
| V | 5 | end | + add | 1994 |
| MCMXCIV = 1994 | ||||
The six subtractive pairs
I can sit before V or X, X before L or C, and C before D or M. Nothing else subtracts, so 99 is XCIX and never IC.
IV
4
5 − 1
not
IIIIIX
9
10 − 1
not
VIIIIXL
40
50 − 10
not
XXXXXC
90
100 − 10
not
LXXXXCD
400
500 − 100
not
CCCCCM
900
1000 − 100
not
DCCCC
Seven letters, and a bar for the big numbers
Everything is built from these seven letters. A bar drawn over a letter multiplies it by 1,000, which is how numerals past 3,999 get written. You will mostly meet the bar in old legal records and formal inscriptions.
Smallest to largest, one way to remember them:
I Value Xylophones Like Cows Dig Milk
- I1A single stroke, the oldest tally mark.
- V5Often explained as an open hand.
- X10Commonly read as two Vs meeting at the point.
- L50Thought to be half of an older sign for 100.
- C100From centum, Latin for hundred.
- D500Thought to be half of an old sign for 1,000.
- M1,000From mille, Latin for thousand.
With a bar on top
V
5,000
X
10,000
C
100,000
M
1,000,000
Numerals you are likely to run into
IV as a number
4
Clocks often print IIII instead. Both mean 4.
XLII as a number
42
XL is 40 (50 − 10), then II adds 2.
MCMXCIV as a number
1,994
Three subtractions (CM, XC, IV) hidden inside seven letters.
MMXXVI as a number
2,026
2000 + 20 + 6. Nothing is subtracted.
LXIII as a number
63
L is 50, X is 10, III is 3. Common in chapter numbers.
MMMCMXCIX as a number
3,999
The largest numeral without a bar: nine letters, three subtractive pairs.
Questions people ask
Reading rules, invalid numerals, batch decoding and the clock oddity.
Go left to right. If a letter is smaller than the one after it, subtract it; otherwise add it. In IX the I is smaller than the X, so it is 10 − 1 = 9. In XI the X is bigger than the I, so it is 10 + 1 = 11.
