Roman Numeral Converter

Roman numerals are the oldest number system still in daily use - chapter headings, clock faces, film credits, monarchs and outline hierarchies all still speak it. The system is simple: seven symbols, additive values, one subtraction rule for the fours and nines. Simple enough to read, but the conversion in either direction is exactly where people trip - "IC" looks like 99 to a beginner and is nonsense to a purist.

Roman Numeral Converter converts exactly in both directions, with strict validation and a place-by-place breakdown. Numbers from 1 to 3999 become their proper roman form, roman strings like MCMLXXXIV become 1984 with every group explained, and invalid strings are rejected with the reason. The rules are applied the way the ancients - and the textbook - intended.

• Both directions: Number to roman and roman to number.
• Strict validation: "IIII" and "IC" are rejected, not guessed.
• Place-by-place breakdown: Every symbol group explained.
• Full classic range: 1 to 3999, the standard system.
• Instant conversion: Results appear as you type.
• Copy or download: Ready for documents and homework.
• Free and private: Everything runs in your browser; nothing is uploaded.

1. Choose the direction - number to roman, or roman to number.
2. Enter the value - digits for one direction, roman symbols for the other.
3. Read the converted result instantly.
4. Study the breakdown showing how each group of symbols adds up.
5. Fix invalid roman strings - the tool explains what is wrong.
6. Copy or download the result.

Example 1 - The year. Convert 1984 to roman: MCMLXXXIV. The breakdown shows M (1000) + CM (900) + LXXX (80) + IV (4).

Example 2 - The small ones. Convert 4 to IV, 9 to IX, 40 to XL, 90 to XC, 400 to CD and 900 to CM - the six subtraction pairs, each one clean.

Example 3 - Max. Convert 3999: MMMCMXCIX - the largest value the classic system can write with standard rules.

Example 4 - Reverse. Paste MCMLXXVI: 1976, with each group explained line by line.

Example 5 - Invalid input. Paste "IC". The tool rejects it and explains that I cannot precede C - 99 is correctly XCIX.

• Exact in both directions: No guessing, no partial conversions.
• Educational breakdown: See how every symbol contributes.
• Strict rules: Invalid strings rejected with explanations.
• Everything explained: The subtraction pairs are visible in every result.
• Instant and live: No button presses, no waiting.
• Free and private: Runs entirely in the browser with nothing uploaded.