Roman Numeral Converter

Convert a number into Roman numerals or read a Roman numeral back as a number, with the breakdown shown.

Type in either box. Roman input is validated properly, so IIII and IC are rejected rather than quietly misread.

Conversion

—

    How Does It Work?

    1. Type in either boxEnter an ordinary number to get the numeral, or type a numeral to read it as a number. Whichever box you edit, the other updates.
    2. Read the breakdownEach symbol and subtractive pair is listed with its value, so you can see how the total is assembled rather than just trusting it.
    3. Watch for invalid inputOnly correctly formed numerals are accepted. IIII, VX and IC are rejected with an explanation instead of being silently misread.

    What Is It Used For?

    Roman numerals build a number from seven letters, read left to right and added together — except when a smaller value sits before a larger one, which means subtract. That subtractive rule is where mistakes creep in: only six pairs are valid (IV, IX, XL, XC, CD and CM), so 99 is XCIX and never IC. The system also has no zero and no standard way of writing numbers above 3,999 without an overline, which is why converters stop there.

    • Reading a copyright date or a cornerstone inscription.
    • Working out which Super Bowl or Olympiad a numeral refers to.
    • Checking a numeral before committing it to a tattoo or an engraving.
    • Numbering chapters, appendices or clauses in a formal document.
    • Helping with homework, where the subtractive rule is the part that trips people up.

    Examples

    NumberRoman numeralNote
    4IVSubtractive: not IIII
    9IXSubtractive: not VIIII
    99XCIXNot IC — only six pairs are valid
    1994MCMXCIVM + CM + XC + IV
    2026MMXXVIMM + XX + V + I
    3999MMMCMXCIXThe largest without an overline

    Frequently Asked Questions

    What are the Roman numeral symbols?

    Seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. Everything else is built by combining them in descending order, with six subtractive exceptions.

    Why is 99 written XCIX and not IC?

    Only six subtractive pairs are valid: IV, IX, XL, XC, CD and CM. A symbol may only be placed before one of the next two larger values, so I can precede V and X but never C. 99 is therefore XC (90) followed by IX (9).

    How high do Roman numerals go?

    3,999 using ordinary letters, because M can only be repeated three times. Beyond that the Romans drew a bar over a numeral to multiply it by a thousand, a notation with no single agreed digital form — which is why this converter stops at 3999.

    Is there a Roman numeral for zero?

    No. The system counts things and had no need for a placeholder digit, which is precisely why arithmetic in Roman numerals is so awkward and why positional decimal notation replaced it.

    How do I write a date in Roman numerals?

    Convert each part separately — day, month and year — and join them, usually with dots or slashes. 15 June 2026 becomes XV.VI.MMXXVI. Convert the year on its own if that is all you need.

    Free. No registration. This tool runs entirely in your browser, so the data you enter stays on your device.

    Percentage Calculator

    Work out a percentage of a number, a percentage share, or a percentage change.

    Random Number Generator

    Pick random numbers in any range, with or without repeats.

    Day of the Week

    Find what day of the week any date falls on, past or future.

    Uppercase / Lowercase Converter

    Change text to UPPERCASE, lowercase, Title Case and more.