Roman Numeral Converter
Convert decimal numbers and Roman numerals in either direction.
Standard Roman notation supports whole numbers from 1 through 3999.
Roman numeral
About the Roman Numeral Converter
The Roman Numeral Converter translates whole decimal numbers into standard Roman notation and converts Roman numerals back into decimal values. For example, 2026 becomes MMXXVI, and MMXXVI becomes 2026.
Roman numerals combine the symbols I, V, X, L, C, D and M. Standard notation places larger values before smaller ones, with subtractive pairs such as IV for 4, IX for 9, XL for 40 and CM for 900.
Validation checks the complete numeral rather than adding symbol values blindly. Non-standard forms such as IIII, VX and IIV are rejected with a clear message instead of producing a misleading result.
This tool supports the conventional modern range from 1 through 3999, written as I through MMMCMXCIX. Roman notation has no universally standardized symbol for zero or negative numbers.
Key features
- Decimal to Roman numeral conversion
- Roman numeral to decimal conversion
- Strict standard-syntax validation
- Case-insensitive Roman numeral input
- One-click result copying
How to use
- 1Choose Decimal to Roman or Roman to decimal.
- 2Enter a whole number from 1 through 3999, or a standard Roman numeral from I through MMMCMXCIX.
- 3Read the live result and use Copy result when needed.
Frequently asked questions
- What is 2026 in Roman numerals?
- 2026 is MMXXVI: MM is 2000, XX is 20 and VI is 6.
- What number is MMXXVI?
- MMXXVI is 2026 in decimal notation.
- Why is IIII rejected?
- Standard modern notation writes 4 as IV. The converter rejects non-standard repetitions and invalid subtractive combinations.
- What range does the converter support?
- It supports whole numbers from 1 through 3999. This is the conventional range that uses the standard seven Roman numeral letters without overlines or extended symbols.
- Can Roman numerals represent zero?
- Classical Roman numerals do not have a standard symbol for zero, so this converter begins at 1.