Roman Numeral Converter

Turn a number into Roman numerals or read a Roman numeral back as a number — with proper validation across the classic 1–3999 range.

🔒 100% private — nothing is uploaded

The seven symbols

I1
V5
X10
L50
C100
D500
M1000

How Roman numerals work

Seven letters combine to build every number from 1 to 3999. Symbols are written largest-first and added up — except for the six subtractive pairs, where a smaller symbol in front of a larger one is subtracted.

1

Number → Roman

Type any whole number from 1 to 3999 and see its Roman form built with the standard additive and subtractive rules (like IV for 4 and IX for 9).

2

Roman → Number

Type a numeral in any case. It's validated against strict formation rules — malformed strings like IIII or VX are flagged rather than silently misread.

3

Copy & use

Grab the result with the Copy button for titles, clock faces, outlines, movie credits or dates — nothing is ever saved or sent anywhere.

Rules and limits

The six subtractive pairs are the only places a smaller symbol precedes a larger one: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Everywhere else, symbols are added left to right. A symbol can repeat at most three times in a row, which is why 4 is IV rather than IIII.

Standard Roman numerals have no symbol for zero and no way to write negatives or fractions, and the largest value expressible without overline notation is 3999 (MMMCMXCIX). This tool therefore accepts whole numbers from 1 to 3999 and only recognises strictly well-formed numerals when converting back.

🔒

Private by design. Every conversion happens right here in your browser with plain JavaScript. Nothing you type is ever uploaded or stored — we never see it.

Frequently Asked Questions

What are the seven Roman numeral symbols and their values? ▼
There are seven letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. They are normally written largest-first and added together.
How does subtractive notation work? ▼
In six specific pairs a smaller symbol is placed before a larger one and subtracted: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). This is why 4 is written IV rather than IIII — a symbol may repeat at most three times in a row.
What range of numbers can be converted? ▼
The classic system covers whole numbers from 1 to 3999. Values above that traditionally need an overline (a bar meaning ×1000), which this tool doesn't use, so it accepts 1–3999 (3999 being MMMCMXCIX).
Why is there no Roman numeral for zero? ▼
Roman numerals are an additive tally system with no place value, so there was never a symbol for zero — and no way to write negative numbers or fractions either. Counting simply starts at I (1).
Does capitalisation matter, and are invalid numerals caught? ▼
You can type in any case — mmxxvi and MMXXVI are read the same. Malformed strings such as IIII or VX are rejected rather than silently misread, because the tool checks each numeral against strict formation rules.

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