gizmobench

Roman Numeral Converter

Type a number or a roman numeral and the direction is worked out for you. The answer comes with its breakdown, so MCMXCIV reads as M + CM + XC + IV rather than a wall of letters. A full reference chart and the six subtractive pairs sit below the converter, and malformed numerals get told exactly which rule they break.

Roman numeral converterReadyType a number or a roman numeral, and the direction is detected
Number or numeral

Roman numerals chart

Click any value to load it above.

1 to 10

1
2
3
4
5
6
7
8
9
10

11 to 20

11
12
13
14
15
16
17
18
19
20

Tens

10
20
30
40
50
60
70
80
90
100

Hundreds

100
200
300
400
500
600
700
800
900
1,000

Thousands

1,000
2,000
3,000

The six subtractive pairs

These are the only cases where a smaller symbol goes before a larger one. Every other combination (IC, XM, VX) is invalid, which is why they are rejected above.

  • IV1 before 5
    4
  • IX1 before 10
    9
  • XL10 before 50
    40
  • XC10 before 100
    90
  • CD100 before 500
    400
  • CM100 before 1000
    900

Common questions

Why is 4 written IV and not IIII?
Because of subtractive notation: a smaller symbol placed before a larger one is subtracted from it, so IV is 5 − 1. Only six subtractive pairs are valid: IV, IX, XL, XC, CD and CM. You will still see IIII on clock faces, a long-standing typographic tradition rather than a different rule.
Is there a roman numerals chart?
Yes. The full chart is on this page, below the converter: 1 to 20 individually, then the tens, hundreds and thousands. Every entry is clickable and loads into the converter, so you can go from the chart straight to a breakdown of how that value is built.
What is the largest number roman numerals can write?
3,999 (MMMCMXCIX) in the standard system, because M is the largest symbol and no symbol repeats more than three times. Larger values historically used a vinculum, an overbar meaning multiply by 1,000, which has no single agreed plain-text form. This converter says so rather than inventing one.
Why is there no zero?
The system was built for counting and tallying, where nothing simply is not written. Roman numerals have no symbol for zero and no way to express negative numbers or fractions of the kind positional systems handle naturally, which is one of the reasons Hindu-Arabic numerals displaced them for arithmetic.
Which repeated symbols are allowed?
I, X, C and M may repeat up to three times in a row. V, L and D are never repeated, because two of them would always equal the next symbol up. VV is simply X. Anything breaking those rules gets rejected here with the specific reason and the correct form.
How do I read a long numeral like MCMXCIV?
Break it into pieces from the left, taking subtractive pairs as single units: M (1000) + CM (900) + XC (90) + IV (4) = 1994. The breakdown shown on this page does exactly that, which is usually faster than trying to read the whole string at once.
Is lowercase acceptable?
Formally numerals are uppercase, but lowercase appears widely in page numbering and outlines. Lowercase input is accepted here and normalised, so mcmxciv and MCMXCIV both work.

Exact for the standard subtractive notation from 1 to 3,999, which is the range classical Roman numerals define. Values above that require overline notation for thousands, which has no single agreed plain-text form, and the tool says so rather than inventing one.