Roman numerals

About this tool

Roman numeral converter: what it is and how to use it

Roman numerals write numbers with seven letters: I, V, X, L, C, D and M. This free converter turns a number into Roman numerals, or a numeral back into a number, as you type, for 1 to 3,999, and shows the working place by place. It runs in your browser and saves nothing.

How Roman numerals work

The Cambridge Dictionary describes Roman numerals as the letters that the ancient Romans used to write numbers. Seven letters do all the work: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000.

Read from left to right, letters of equal or falling value add up, so XV is 15 and MDC is 1,600. When a smaller letter sits just before a larger one, it is taken away instead: IV is 4 and XC is 90. The standard form this converter uses has six of these pairs: IV, IX, XL, XC, CD and CM.

The simplest way to write any number is place by place. Split it into thousands, hundreds, tens and ones, write each part with its letters, then join them from left to right. The standard form shown here covers 1 to 3,999. If you type a numeral that is not in standard form, such as IIII, the converter reads it letter by letter and shows the standard way to write the same number.

How to use it

1. Type a whole number from 1 to 3,999 in the Number box, or press This year.
2. Or type a numeral in the Roman numeral box, using the letters I, V, X, L, C, D and M. Small or capital letters both work.
3. Read How it adds up: the number split into thousands, hundreds, tens and ones, with the letters for each part.
4. Check the two tables of the seven letters and the six subtractive pairs, then use the Copy buttons to take the result with you.

An example

Say you are making a birthday card for a friend born in 1987 and want the year in Roman numerals. Type 1987. The converter shows MCMLXXXVII and the working underneath: M for 1,000, CM for 900, LXXX for 80 and VII for 7. Press Copy numeral and paste it into your design.