What is the largest Roman numeral?

This tool supports numbers up to 3999 (MMMCMXCIX). Larger values were historically written with a bar over the letters, which is not standard modern notation.

Why is IIII not accepted?

In the standard system 4 is written IV. IIII sometimes appears on clock faces, but is generally treated as non-standard, so the tool shows the correct form.

Is there a Roman numeral for zero?

No. The Roman system had no zero, so the smallest number is I (1).

Is my data sent to a server?

No, everything is calculated in your browser.

Roman Numeral Converter

Convert numbers 1–3999 to Roman numerals and back – the result updates as you type.

Number to Roman numeral

Number (1–3999)

Roman numeral to number

Roman numeral

How to use it

On the left, enter a number from 1 to 3999 and the Roman numeral appears instantly. On the right, enter a Roman numeral (upper or lower case) to get the ordinary number. Copy any result with one click.

I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.
A smaller symbol before a larger one is subtracted: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.
The standard form never repeats a symbol more than three times in a row (III = 3, but 4 is IV).

Non-standard numerals

If you enter a malformed numeral such as IIII, VX or IC, the tool does not silently accept it. It shows the standard form of that value instead (IIII becomes IV), which makes copy-paste mistakes easy to spot.

The standard Roman system has no zero and no negative numbers, and 3999 (MMMCMXCIX) is the largest value without special notation, hence the range 1 to 3999.

Where Roman numerals are used

Centuries (XXI century), book chapters and volumes, monarch names (Elizabeth II), clock faces, and film or sporting event numbers. Calculations run in your browser and nothing you enter is sent anywhere.