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Roman Numeral Converter

Convert numbers to Roman numerals and back.

How it's built

M (1000) + M (1000) + X (10) + X (10) + V (5) + I (1)

Roman numeral symbols

I

1

V

5

X

10

L

50

C

100

D

500

M

1000

When to use it

Use this tool to convert numbers to Roman numerals and back. It is useful for reading dates on buildings and film credits, writing years for tattoos, invitations or certificates, numbering book chapters and outlines, understanding clock faces, and checking homework.

How to use it

  1. Type a whole number from 1 to 3999 in Number to see it as a Roman numeral.
  2. Or type a numeral in Roman numeral, using I, V, X, L, C, D and M, to see the number.
  3. Read How it’s built, which breaks the numeral into its parts.
  4. Click Copy Roman numeral to copy it.
  5. Check the Roman numeral symbols table if you need a reminder.

Worked example

The default number is 2026. It becomes MMXXVI, built as M (1000) + M (1000) + X (10) + X (10) + V (5) + I (1).

Going the other way, a film’s credits end with MCMXCIX. Type it into Roman numeral and the number is 1999, built as M (1000) + CM (900) + XC (90) + IX (9). CM, XC and IX are the subtractive pairs: 1000 − 100, 100 − 10 and 10 − 1.

If you type IIII, the tool explains that it is not standard form and suggests IV instead.

How to read Roman numerals

Read from left to right and add the values. When a smaller symbol comes before a larger one, subtract it instead. So VI is 5 + 1 = 6, while IV is 5 − 1 = 4.

Only these subtractive pairs are used: IV, IX, XL, XC, CD and CM. A symbol is never repeated more than three times in a row.

Where Roman numerals are still used

You will see them on clock faces, in the names of monarchs and popes such as Elizabeth II, for big events like the Olympic Games and the Super Bowl, in movie copyright years, and for page numbers at the front of books.

Tips

  • Break big numbers into parts. For 1987, write 1000 (M), 900 (CM), 80 (LXXX) and 7 (VII) to get MCMLXXXVII.
  • Check before engraving. For tattoos, rings and plaques, copy the numeral rather than typing it by hand.
  • Use the steps to learn. They show exactly which symbols make up each number.

Common mistakes

  • Writing 99 as IC. The correct form is XCIX (90 + 9).
  • Writing 1990 as MXM. The correct form is MCMXC.
  • Repeating V, L or D. These are never doubled. 10 is X, not VV.

Frequently asked questions

What is the largest Roman numeral?

In standard form, 3999, written MMMCMXCIX. Larger numbers were written with a bar over a letter to multiply it by 1,000, but there is no single agreed modern form, so the tool stops at 3999.

Is there a Roman numeral for zero?

No. The Roman system had no symbol for zero, so the converter works from 1 upwards.

Why is 4 written IV and not IIII?

Standard Roman numerals use subtraction for 4 and 9 at each level: IV is 5 − 1, IX is 10 − 1, XL is 40, XC is 90, CD is 400 and CM is 900. IIII appears on some clock faces for style, but IV is the standard form.

What if I type a non-standard numeral?

The tool tells you it is not in standard form, works out what it probably means, and shows the correct way to write it. For example, IIII is read as 4, correctly written IV.

Can I type lowercase letters?

Yes. Lowercase numerals like xiv are accepted and shown in capitals.

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