# Roman Numeral Converter

> Roman numeral converter: translate decimal numbers to Roman numerals and Roman numerals back to numbers instantly, for values up to 3999. Free, no signup.

- **Canonical URL:** https://boringtoolskit.com/roman-numeral-converter/
- **Category:** Converters
- **Evidence level:** authored-methodology
- **Reviewed:** 2026-09-20
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

Greedy subtraction over the value table M (1000), CM (900), D (500), CD (400), C (100), XC (90), L (50), XL (40), X (10), IX (9), V (5), IV (4), I (1): take the largest symbol that fits, repeat until the value is consumed. Reading back subtracts a smaller symbol when it precedes a larger one.

## Assumptions

- Inputs are treated as exact decimal values.
- Standard (not historical or survey) unit definitions are used.
- The calculation uses the factors at the precision shown in the formula panel; rounding beyond that is display-only and adds no accuracy.

## Common questions

### What is the valid range for Roman numerals here?

The tool accepts 1 to 4999. There is no standard symbol for 5000 or larger in the classical set, so values outside that range are rejected instead of approximated.

## Sources

- [Number Forms (U+2150-U+218F) - roman numeral symbols](https://www.unicode.org/charts/PDF/U2150.pdf)
- [Roman numerals - subtractive notation and range](https://en.wikipedia.org/wiki/Roman_numerals)

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