How large can Roman numerals go?

Standard notation covers 1 to 3999. Larger values need an overline meaning ×1000, which is rarely used on the web and is not supported here.

Why is IIII rejected?

In standard notation a symbol repeats at most three times, so 4 is IV. The tool regenerates the numeral to check it and flags non-standard spellings.

What is the subtraction rule?

A smaller symbol before a larger one subtracts, and only six pairs are allowed: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.

Is there a Roman numeral for zero?

No — the system has no symbol for zero, so only whole numbers from 1 upwards can be written.

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🏛️Roman Numeral Converter - Numbers to Roman Numerals and Back

The same box takes either a number or a Roman numeral and converts in the right direction automatically. Every result is broken down symbol by symbol, with a reference table and the subtraction rules alongside.

Free · No sign-up · Runs in your browserLast updated: 2026-10-26

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How to use Roman Numerals

1Type a number (2024) or a Roman numeral (MMXXIV)
2The conversion and the breakdown appear instantly
3Copy the result in one click

FAQ

How large can Roman numerals go?: Standard notation covers 1 to 3999. Larger values need an overline meaning ×1000, which is rarely used on the web and is not supported here.
Why is IIII rejected?: In standard notation a symbol repeats at most three times, so 4 is IV. The tool regenerates the numeral to check it and flags non-standard spellings.
What is the subtraction rule?: A smaller symbol before a larger one subtracts, and only six pairs are allowed: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
Is there a Roman numeral for zero?: No — the system has no symbol for zero, so only whole numbers from 1 upwards can be written.