Roman Numeral Converter
Convert numbers to Roman numerals and back. Supports 1–3999. Includes a reference chart for common values.
Reference Chart
| Number | Roman |
|---|---|
| 1 | I |
| 4 | IV |
| 5 | V |
| 9 | IX |
| 10 | X |
| 14 | XIV |
| 40 | XL |
| 50 | L |
| 90 | XC |
| 100 | C |
| 400 | CD |
| 500 | D |
| 900 | CM |
| 1,000 | M |
| 1,776 | MDCCLXXVI |
| 1,999 | MCMXCIX |
| 2,024 | MMXXIV |
| 3,999 | MMMCMXCIX |
Symbol Values
I
1
V
5
X
10
L
50
C
100
D
500
M
1000
How to Use Roman Numeral Converter
- 1Enter a number (1–3999) to convert to Roman numerals.
- 2Or enter Roman numerals to convert back to a number.
- 3Copy the result.
- 4Browse the reference chart for common values.
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Frequently Asked Questions
How do Roman numerals work?▾
Roman numerals use 7 symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Numbers are formed by combining symbols from largest to smallest, left to right. Subtractive notation: when a smaller value precedes a larger one, it is subtracted — IV = 4 (5-1), IX = 9 (10-1), XL = 40, XC = 90, CD = 400, CM = 900. This subtractive convention was standardized in medieval Europe.
Why do Roman numerals stop at 3999?▾
Standard Roman numerals (without overlines or parentheses) go up to MMMCMXCIX (3999). The Romans used an overline (vinculum) above a numeral to multiply it by 1000, extending the range. Modern applications typically limit to 3999 for simplicity. Technically, clock faces often use IIII instead of IV for 4, as it looks more balanced.
Where are Roman numerals used today?▾
Roman numerals appear on clock faces, movie sequels and series (Star Wars Episode IV), book chapters, Super Bowl numbering, Olympic Games, architectural inscriptions and cornerstones (dates), page numbering in book front matter, legal code sections, and formal outlines. They are also used in astronomy (Galilean moons: Io is Jupiter I) and music theory (chord numerals).
What is the largest number in Roman numerals without extensions?▾
3999, written as MMMCMXCIX. To represent 4000 and above, the Roman system historically used a bar over a numeral (vinculum) to multiply by 1,000: V̄ = 5,000, X̄ = 10,000, L̄ = 50,000, C̄ = 100,000, D̄ = 500,000, M̄ = 1,000,000. Some uses also employed parentheses: (V) = 5,000. These extensions are not commonly used in modern contexts.
How do I convert Roman numerals to integers in code?▾
Scan left to right. If the current value is less than the next value, subtract it (subtractive rule); otherwise add it. In Python: values = {I:1, V:5, X:10, L:50, C:100, D:500, M:1000}; result = 0; for i in range(len(s)): result += (-1 if i+1 < len(s) and values[s[i]] < values[s[i+1]] else 1) * values[s[i]]. The same logic works in any language.