BrowserTools

Roman Numeral Converter

Numbers to Roman numerals and back

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-14
Free Private No uploads
What is Roman Numeral Converter?

Roman numerals are built from seven letters — I, V, X, L, C, D and M — with a subtractive convention that lets a smaller letter before a larger one subtract: IV is four, not six. The standard written form runs from 1 to 3999, and anything above that needs an overbar to multiply a thousand, so a hard ceiling is a property of the notation rather than a limit of this tool. The other direction is more forgiving. The parser ignores case and discards every character outside the seven letters before applying the subtract-if-smaller rule, which means it will happily return a number for text that was never a valid numeral. The two directions sit on separate tabs, each with its own input and a result box beneath it.

Convert numbers to Roman numerals (I, V, X, L, C, D, M) and parse Roman numerals back to numbers. Great for classwork, tattoos double-checking, copyright dates and puzzle solving.

Private Roman Numeral Converter In Your Browser

Roman Numeral Converter is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use Roman Numeral Converter

1

Open the Number → Roman tab and type an integer between 1 and 3999 into the number field.

2

Read the numeral in the result panel below the field.

3

For the reverse, switch to the Roman → Number tab and type the numeral, in upper or lower case.

4

Check the returned integer, keeping in mind the parser is permissive about non-standard forms.

Key Capabilities
  • Number to numeral covers the full standard range of 1 to 3999
  • Numeral to number accepts upper or lower case and ignores surrounding text
  • Out-of-range numbers are refused with an explanation rather than truncated
  • Both directions on separate tabs with independent inputs
Common Use Cases
  • A teacher preparing the worked examples for a lesson on Roman numeral place value and subtraction.
  • A designer setting a book or film title that uses a Roman numeral year and confirming the number.
  • A crossword solver testing whether a clue's answer is a numeral rather than a word.
Clear Answers

Frequently Asked Questions

Why does it stop at 3999?
Because the conventional notation does. Above 3999 the letters would repeat without bound — 4000 is normally written with a bar over the IV, and 4000 with an overlined V. Those forms are rare enough that the tool treats them as out of range rather than guessing at an overline, and the number you typed must be 3999 or below.
What happens if I enter non-standard numerals like IIII?
You get a number back, because the parser is deliberately permissive. It upper-cases the text, throws away anything that is not one of the seven letters, then adds each letter unless the following one is larger, in which case it subtracts it. IIII therefore reads as 4, and VX reads as 5. Both are non-standard forms, so check the input if the result looks strange.
Is there a zero?
No, and there is no place for one. Roman numerals record value by adding and subtracting letters, so there is no symbol that represents nothing, which is one reason the system never displaced positional notation. Typing 0 is rejected along with every other value outside 1 to 3999.
Why did pasting a sentence give me a number?
Because the parser strips everything that is not one of the seven letters before evaluating. I, V, X, L, C, D and M turn up inside ordinary words often enough that a sentence can easily produce a plausible-looking integer. Feed it numerals when you want a reliable answer.