Roman Numeral Converter
Convert integers (1 to 3999) to Roman numerals or parse Roman numerals back to numbers with canonical validation and a step-by-step breakdown.
Private by architecture:
All processing is 100% client-side memory. Your data never leaves this browser tab.
Converted result
- Roman numeral
- MCMXCIV
- Integer value
- 1994
- Canonical status
- Canonical
1..3999 range
Step-by-step breakdown
| Symbol | Value | Count | Subtotal | Running total |
|---|
About This Tool
Converts whole numbers between 1 and 3999 to standard Roman numerals (I to MMMCMXCIX) and parses Roman numerals back into integers. Auto-detects whether your input is a number or a Roman numeral.
Displays a step-by-step table showing every symbol group (M, CM, D, CD, C, XC, L, XL, X, IX, V, IV, I), its multiplier, subtotal, and running total.
Key Features
- Auto-detected bidirectional input: Type either an integer (like 1994) or a Roman numeral (like MCMXCIV) and get the converted result immediately.
- Strict canonical validation: Flags non-standard numerals such as IIII, VV, or IC and shows the exact canonical replacement (IV, X, XCIX).
- Step-by-step breakdown: Lists each additive and subtractive token with its numeric value, count, subtotal, and running sum.
- Relaxed clock-face mode: Uncheck strict validation when decoding additive inscriptions such as IIII on clock dials.
Frequently Asked Questions
Why is the maximum canonical Roman numeral 3999 (MMMCMXCIX)?
In standard Roman notation without vinculum overlines, M (1000) is the largest symbol and no symbol can repeat more than three times consecutively. That makes MMMCMXCIX (3000 + 900 + 90 + 9 = 3999) the highest representable value.
What makes a Roman numeral non-canonical?
Canonical rules forbid repeating V, L, or D, forbid repeating I, X, C, or M more than three times in a row, and restrict subtractive pairs to IV, IX, XL, XC, CD, and CM. Forms like IIII (4) or IC (99) violate these rules.
Does this tool run offline?
Yes. All parsing and validation run locally in your browser with no server requests.
