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ローマ数字変換ツール

アラビア数字とローマ数字の間で変換します。

はじめに

Roman Numeral Converter — Convert between Arabic numbers and Roman numerals. Enter Convert, Number to get an instant, accurate result.

計算式

Arabic to Roman: the number is greedily reduced using standard numeral values (M=1000, CM=900, D=500, CD=400, C=100, XC=90, L=50, XL=40, X=10, IX=9, V=5, IV=4, I=1), appending the largest matching symbol repeatedly. Roman to Arabic: values are summed left to right, subtracting a symbol whose value is less than the symbol immediately after it.

ステップごとの説明

  1. Enter the Convert.
  2. Enter the Number.
  3. Click Calculate to see your result instantly.

実例

Example: With Convert = to_roman, Number = 1994, the Roman Numeral Converter gives Roman: MCMXCIV.

よくある質問

What range of numbers is supported?
Standard Roman numerals represent values from 1 to 3,999; there is no standard symbol for 0 or numbers of 4,000 and above.
How do subtractive pairs like IV and IX work?
A smaller numeral placed before a larger one is subtracted from it — IV is 5−1=4, IX is 10−1=9 — rather than always adding left to right.
What inputs does the Roman Numeral Converter need?
You'll need to provide: Convert, Number. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Roman Numeral Converter?
The Roman Numeral Converter applies the formula exactly as calculated — Arabic to Roman: the number is greedily reduced using standard numeral values (M=1000, CM=900, D=500, CD=400, C=100, XC=90, L=50, XL=40, X=10, IX=9, V=5, IV=4, I=1), appending the largest matching symbol repeatedly. Roman to Arabic: values are summed left to right, subtracting a symbol whose value is less than the symbol immediately after it. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Roman Numeral Converter free to use?
Yes, the Roman Numeral Converter is completely free, requires no signup, and runs instantly in your browser.

ローマ数字変換ツールについて

The Roman Numeral Converter uses a real, verifiable formula — Arabic to Roman: the number is greedily reduced using standard numeral values (M=1000, CM=900, D=500, CD=400, C=100, XC=90, L=50, XL=40, X=10, IX=9, V=5, IV=4, I=1), appending the largest matching symbol repeatedly. Roman to Arabic: values are summed left to right, subtracting a symbol whose value is less than the symbol immediately after it. — so results are accurate every time, not an approximation.