What is the maximum number supported?

Up to 3,999,999. Numbers above 3,999 use vinculum notation — a bar over the numeral that multiplies its base value by 1,000.

What is vinculum notation?

Vinculum (overline) notation extends Roman numerals beyond 3,999 by placing a bar over a symbol to multiply it by 1,000. For example, V̄ = 5,000.

Can I convert Roman numerals back to decimal?

Yes — the tool works both ways. Enter a Roman numeral string and it will display the corresponding decimal number.

What is stored in the history?

The last 20 conversions you performed are stored in localStorage. Each entry shows both the decimal and Roman numeral form.

Is zero or negative numbers supported?

No. Roman numerals do not include zero or negative values, so the tool only accepts integers from 1 to 3,999,999.

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Number to Roman Numeral Converter

Convert numbers to Roman numerals and back — supports up to 3,999,999 with vinculum.

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このツールについて

Number to Roman Numeral Converter handles the full range from 1 to 3,999,999 using vinculum notation (a bar over a numeral multiplies its value by 1,000) for large numbers. Type any decimal integer to see the Roman numeral instantly, or enter a Roman numeral to convert it back to decimal. The last 20 conversions are shown in a history list with one-click copy. A built-in reference table lists all standard Roman numeral symbols and their values for quick lookup.

使い方

1 Enter a decimal number (1–3,999,999) in the input field.
2 See the Roman numeral result instantly below.
3 Switch to Roman-numeral input mode to convert back to decimal.
4 Click the copy icon to copy the result to your clipboard.
5 Scroll down to view the reference table of Roman numeral symbols.

このツールについて

使い方

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