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.