Roman Numeral Converter
Convert between decimal numbers and Roman numerals (1-3999).
What is the Roman Numeral Converter?
The Roman Numeral Converter is a free online tool that converts between decimal numbers and Roman numerals in both directions. Enter a number to get its Roman numeral, or enter a Roman numeral to get its decimal value.
It uses standard Roman numeral rules, including subtractive notation such as IV for 4 and CM for 900, and supports the valid range of 1 to 3999. Numbers outside that range return an out-of-range message because classical Roman numerals have no symbol for zero or for values above 3999.
Conversion happens instantly as you type and runs entirely in your browser. There is no signup and no data is sent to a server.
How to use the Roman Numeral Converter
- 1Enter a whole number between 1 and 3999 in the Decimal Number field to see its Roman numeral appear immediately.
- 2Alternatively, type a Roman numeral using the letters I, V, X, L, C, D, and M in the Roman Numeral field to get the decimal value.
- 3Note that Roman input is automatically converted to uppercase as you type.
- 4Use the example buttons, such as Year 2024 or 999, to load common conversions quickly.
- 5Check the highlighted summary card that shows the decimal and Roman values side by side, and press Ctrl+L to clear both fields.
What you can use it for
- Working out the Roman numeral for a copyright year or movie release date.
- Converting Roman numerals found on clock faces, book chapters, or building inscriptions into ordinary numbers.
- Generating Roman numeral labels for document outlines and section headings.
- Checking answers while studying or teaching how subtractive notation like IX and XL works.
- Producing Roman numerals for design work such as posters, certificates, or event branding.
Key features
- Two-way conversion between decimal numbers and Roman numerals.
- Live results that update as you type, with no convert button to press.
- Automatic uppercasing of Roman numeral input for convenience.
- Clear out-of-range messaging for values outside the supported 1 to 3999 range.
Frequently asked questions
How do I convert a number to a Roman numeral?
Type a whole number between 1 and 3999 into the Decimal Number field. The tool instantly builds the Roman numeral using standard symbols and subtractive notation, for example converting 2024 to MMXXIV.
What is the maximum number this Roman numeral converter supports?
The converter supports numbers from 1 to 3999. Classical Roman numerals have no standard symbol for zero or for values of 4000 and above, so numbers outside this range return an out-of-range message.
How does subtractive notation work in Roman numerals?
Subtractive notation places a smaller numeral before a larger one to subtract it, such as IV for 4, IX for 9, XL for 40, and CM for 900. The converter applies these rules automatically in both directions.
Can I convert a Roman numeral back to a number?
Yes. Type a Roman numeral into the Roman Numeral field using the letters I, V, X, L, C, D, and M. The tool reads it left to right, applies subtractive rules, and shows the decimal value.
Why do Roman numerals have no zero?
The Roman numeral system was designed for counting and has no symbol or place for zero. Because of this, the converter starts at 1 and cannot represent zero or negative numbers.
Is the Roman numeral converter free to use?
Yes. It is completely free, requires no account, and runs entirely in your browser. Conversions happen locally and nothing you enter is sent to a server.