Roman Numeral Converter

This calculator works in both directions, turning Roman numerals into ordinary numbers and ordinary numbers into Roman numerals, so you never need a conversion table by hand. You enter a single value in the box, either a Roman numeral such as MMXXIV or a whole number from 1 to 3999, and the calculator works out which type you have typed and converts it automatically. The main result shows the conversion in full, for example 2024 = MMXXIV, while two smaller results underneath give you the other form on its own and the direction of the conversion, meaning whether you went from a Roman numeral to a number or from a number to a Roman numeral. Behind the scenes the tool applies the standard rules: I, V, X, L, C, D and M stand for 1, 5, 10, 50, 100, 500 and 1000, and a smaller letter placed before a larger one is subtracted rather than added, as in IV for four or XL for forty. Because there is no Roman symbol above M, the calculator only accepts numbers from 1 to 3999, and it checks that anything you type is a properly formed numeral, flagging invalid entries such as IIII rather than guessing at an answer. It suits reading clock faces, book chapters, film credits and formal documents, or checking your own working when learning the system.

Roman numeral or number (1 to 3999)

MMXXIV = 2024

The other form2024

DirectionRoman to number

The formula

The letters are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Values add when written largest first; a smaller value before a larger one is subtracted (IV = 4, IX = 9, XL = 40, CM = 900). The standard range is 1 to 3999.

Worked example

MMXXIV is M + M + X + X + (V minus I) = 1000 + 1000 + 10 + 10 + 4 = 2024. Going the other way, 1984 becomes MCMLXXXIV. Enter MMXXIV to confirm.

Frequently asked questions

How do Roman numerals work?

Letters stand for values that you add when written in descending order. A smaller letter before a larger one is subtracted, like IV for 4.

Why only up to 3999?

Standard Roman numerals have no symbol above M (1000), so the usual range without special bars is 1 to 3999.

Is there a zero in Roman numerals?

No. The Roman system has no symbol for zero.

Who this calculator is for

This calculator is for students, history buffs and anyone reading or writing Roman numerals.

What this calculator assumes

You enter a valid Roman numeral or a whole number from 1 to 3999.
Standard subtractive notation is used.
The numeral is validated for correct form.

Formula and sources

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