How Roman numerals work
Roman numerals build numbers from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. You add letters from largest to smallest, so LX is 60. When a smaller letter sits before a larger one, you subtract it, which is where IV (4) and IX (9) come from. This calculator applies those rules for any whole number from 1 to 3999.
Two examples
The year 2024 becomes MMXXIV: two Ms for 2000, XX for 20, and IV for 4. Read left to right, adding as you go, with the IV subtracting at the end.
The number 49 is XLIX, not IL. Roman numerals only subtract one step at a time, so 40 is XL (ten before fifty) and 9 is IX (one before ten), giving XLIX. This subtraction rule is the part people most often get wrong.
Why the limit is 3999
Standard Roman numerals stop at 3999, written MMMCMXCIX, because there is no single letter for 5000 or more. Larger numbers historically used a bar over a letter to multiply it by a thousand, a notation that does not translate cleanly to plain text, so this converter keeps to the standard range.
Frequently asked questions
Why can't I go above 3999?
Standard Roman numerals have no symbol for 5000 or more. Bigger numbers used a bar over a letter to mean times a thousand, which does not render as plain text, so the converter stops at 3999.
Why is 4 written IV and not IIII?
The subtractive rule: a smaller value before a larger one is subtracted, so IV is 5 minus 1. You will occasionally see IIII on clock faces, but IV is the standard form.
Is there a zero in Roman numerals?
No. The system has no symbol for zero, which is one reason it was eventually replaced for arithmetic by the numerals we use today.
Can it convert Roman numerals back to numbers?
This version goes from numbers to Roman numerals. To read a numeral, add the letters from left to right and subtract any smaller letter that sits before a larger one.