CalcArcade.

Roman Numeral Converter

Choose which way you want to convert, then enter a number or a Roman numeral. You get the converted value and a breakdown of how it is built.

Your numbers

Result

How we calculate it

Roman numerals use the symbols I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. Symbols are written largest first and added, except for six subtractive pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900.

To convert a number, the calculator takes the largest value that fits again and again. For 2024 that is M + M + X + X + IV, which is MMXXIV. Going back, it reads the same parts and adds them.

Assumptions and limits

  • Only the standard form is accepted, so 4 is IV and not IIII, and 99 is XCIX and not IC.
  • The range is 1 to 3999 (I to MMMCMXCIX). Standard Roman numerals have no zero and no symbol for 5000.
  • Letters can be typed in lowercase.

Frequently asked questions

How do I write 4 and 9 in Roman numerals?

Put the smaller symbol before the larger one to subtract it. 4 is IV (5 minus 1) and 9 is IX (10 minus 1).

Why does the converter reject IIII?

Some old clocks use IIII, but the standard form uses IV. The converter accepts only the standard form, so every number has one correct Roman numeral.

What is the largest Roman numeral?

Using the standard symbols, the largest number is 3999, written MMMCMXCIX. Larger numbers need extra notation, such as a bar over a numeral, which is not used here.

Related calculators

Worked example (a fixed example using the starting numbers, it does not change as you type)

Inputs: Convert = Number to Roman numeral; Number (1 to 3999) = 2024.

  • Roman numeral MMXXIV
  • Breakdown M + M + X + X + IV

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Last reviewed: . Formulas and assumptions are described on our methodology page. For information only; not professional advice.