Did the Romans have zero?

No. The Roman numeral system has no symbol for zero. In late Latin the word "nulla" (nothing) was used textually, but never in numeric expressions. Zero as a concept reached Europe through Arab mathematicians in the 13th century along with the positional decimal system we use today.

What is the "subtractive rule"?

When a smaller letter stands before a larger one, it is subtracted: IV = 5−1 = 4, IX = 10−1 = 9, XL = 50−10 = 40, XC = 100−10 = 90, CD = 500−100 = 400, CM = 1000−100 = 900. Only I, X and C may subtract, and only from the two closest larger values.

Why is 4 sometimes written as IIII?

Clock faces often show IIII instead of IV, historically for visual balance across the dial (IIII mirrors VIII on the opposite side). The practice is over 500 years old and appears on Big Ben and modern luxury watches alike.

Can Roman numerals represent fractions?

Yes, historically they used marks like "S" for 1/2 and dots (•) for twelfths: S = 6/12, •••• = 4/12. The system was based on twelfths (unciae) since coins and weights were divided into 12. Today our tool only supports whole numbers.

Roman Numeral Converter (1-3999)

How it works

Enter a number between 1 and 3999 to get it as Roman numerals, or enter Roman numerals to get an Arabic number. Roman numerals use the symbols I (1), V (5), X (10), L (50), C (100), D (500) and M (1000), with subtractive notation like IV (4) and IX (9). Everything is calculated locally in your browser.

About this tool

The Roman numeral converter maps between Arabic numerals (1, 2, 3) and Roman numerals (I, II, III, IV, V, X, L, C, D, M) in both directions. Handy when reading a year on an old building, understanding a title like "Louis XIV", parsing a chapter number in a book, or writing code that handles Roman numerals. We support numbers up to 3,999,999 with extended notation (a line over the letter = x1000). All in the browser, no server dependency.

How to use it

Pick the direction: Arabic → Roman, or Roman → Arabic.
Type the number or the Roman expression.
See the conversion instantly, plus a breakdown of the building blocks.
Copy the result with one click.

Examples

Year 2025

Input2025

OutputMMXXV

King’s number

InputLouis XIV

Output14

Large numbers

Input5000

OutputV̄ (V with a bar = 5·1000)

For numbers over 3999 you must use extended notation (line over the letter). MMMMM (five Ms in a row) is not valid classical Roman.

Common use cases

Read years and dates on old buildings, coins and gravestones.
Understand sequences in historical and papal names (Pius IX, Elizabeth II).
Number front matter and preface pages in books (I, II, III).
Write Super Bowl numbers (Super Bowl LIX = 59).
Teach children about numeral systems in school work.

Frequently asked questions

Did the Romans have zero?: No. The Roman numeral system has no symbol for zero. In late Latin the word "nulla" (nothing) was used textually, but never in numeric expressions. Zero as a concept reached Europe through Arab mathematicians in the 13th century along with the positional decimal system we use today.
What is the "subtractive rule"?: When a smaller letter stands before a larger one, it is subtracted: IV = 5−1 = 4, IX = 10−1 = 9, XL = 50−10 = 40, XC = 100−10 = 90, CD = 500−100 = 400, CM = 1000−100 = 900. Only I, X and C may subtract, and only from the two closest larger values.
Why is 4 sometimes written as IIII?: Clock faces often show IIII instead of IV, historically for visual balance across the dial (IIII mirrors VIII on the opposite side). The practice is over 500 years old and appears on Big Ben and modern luxury watches alike.
Can Roman numerals represent fractions?: Yes, historically they used marks like "S" for 1/2 and dots (•) for twelfths: S = 6/12, •••• = 4/12. The system was based on twelfths (unciae) since coins and weights were divided into 12. Today our tool only supports whole numbers.

Technical background

Roman numerals are an additive/subtractive system with no place value. The symbols are I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Rules: (1) Write from largest to smallest when adding: MCLXVI = 1000+100+50+10+5+1 = 1166. (2) The same letter may repeat at most 3 times (III = 3, but IIII is written IV). (3) Only I, X, C can be used subtractively, only before the two closest larger values: I before V or X (IV, IX), X before L or C (XL, XC), C before D or M (CD, CM). Not valid: IIL, VC. (4) No symbol for zero. (5) For numbers above 3999 there are two systems: vinculum (a line over the letter meaning x1000) or apostrophe notation (I|X = 1M). The tool parses and formats per Unicode’s "Roman Numerals" block (U+2160 to U+2188), which contains precomposed forms like ⅵ (U+2165) and ⅼ (U+217C), but normally uses Latin uppercase for readability. We validate parsing: inputs like IIII, IC, VX or VV are rejected with an error.