Roman numerals

How Roman numerals are read

Roman numerals are built from seven letters: I is one, V five, X ten, L fifty, C a hundred, D five hundred and M a thousand. They add up from left to right, so XVII is ten plus five plus two, that is seventeen.

Subtraction is the exception. When a smaller numeral stands before a larger one it is subtracted: IV is four and IX is nine. Only six pairs may be subtracted, repeating at every order of magnitude: IV, IX, XL, XC, CD and CM. Forms like IL or VX are not used, even though you could read something out of them.

Where you meet them

• Years on buildings, monuments and in books.
• Numbering of chapters, parts and articles in contracts and statutes.
• Watch faces, where four is often written IIII for symmetry.
• Monarchs and popes: Charles IV, John Paul II.
• Film sequels and Super Bowls.

Frequently asked questions

Why does the tool refuse IIII?

Because four is normally written IV. IIII survives only on watch faces, where it is a custom rather than a rule. For such input the tool tells you what the correct form looks like.

How do I write zero or a negative number?

You cannot. The Roman system has no zero (it starts at one) and no negative numbers either. Zero reached Europe with the Arabic numerals.

Why does it stop at 3999?

Larger numbers were written with a bar over the numeral, meaning a multiple of a thousand. That bar is used neither in ordinary text nor in school exercises, so we end at MMMCMXCIX.

Do I have to use capitals?

No. Lower case is accepted and converted to capitals for you, as are extra spaces.