ローマ数字変換器

アラビア数字とローマ数字を即座に変換。1から3999まで対応し、便利な参照表付き。

MMXXIV
アラビア
ローマ
1
I
4
IV
5
V
9
IX
10
X
40
XL
50
L
90
XC
100
C
400
CD
500
D
900
CM
1000
M
すべての変換はブラウザで処理されます。データはサーバーに送信されません。

How to Use This Tool

  1. 1

    Choose conversion direction

    Select "Arabic → Roman" to convert numbers like 2024 to MMXXIV, or "Roman → Arabic" for the reverse.

  2. 2

    Enter your value

    Type an Arabic number (1-3999) or a Roman numeral. The result appears instantly below.

  3. 3

    Try quick examples

    Click any of the quick example buttons to see common conversions immediately.

  4. 4

    Copy the result

    Click "Copy" to copy the converted value to your clipboard.

Frequently Asked Questions

What is the range of Roman numerals?
Standard Roman numerals represent values from 1 (I) to 3999 (MMMCMXCIX). There is no zero or negative numbers in the Roman numeral system.
How does subtractive notation work?
A smaller numeral before a larger one means subtraction: IV = 4 (5-1), IX = 9 (10-1), XL = 40 (50-10), XC = 90 (100-10), CD = 400 (500-100), CM = 900 (1000-100).
Why is 2024 written as MMXXIV?
M=1000, M=1000, X=10, X=10, IV=4. So MMXXIV = 1000 + 1000 + 10 + 10 + 4 = 2024.
Is my data secure?
Yes. All conversion happens entirely in your browser. No data is sent to any server.