Roman Numeral Converter

Convert between Roman and Arabic numerals
This free online roman numeral converter runs in your browser and is part of our Converters collection.

🏛️ Roman Numeral Converter

Convert between Roman numerals and Arabic numbers

Roman Numeral Rules:

  • Basic Symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000
  • Addition: When a smaller value follows a larger, add them (VI = 6)
  • Subtraction: When a smaller value precedes a larger, subtract (IV = 4, IX = 9)
  • Repetition: Symbols can repeat up to 3 times (III = 3, XXX = 30)
  • Range: Standard Roman numerals cover 1-3999

Common Roman Numerals:

I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000
IV = 4
IX = 9
XL = 40
XC = 90
CD = 400
CM = 900
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Instant In-Browser Execution Runs locally in JavaScript without wait times or server delays.
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100% Privacy & Security Your inputs and files are never stored or logged on remote servers.
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Cross-Device Responsive Fully optimized for mobile smartphones, tablets, and desktop displays.
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100% Free Forever No subscription fees, no signups, and no software installations.

How to Use the Online Roman Numeral Converter

1 Choose Conversion Mode

Select "Number to Roman" to convert Arabic integers (e.g. 2026), or "Roman to Number" to decode Roman numerals (e.g. MMXXVI).

2 Input Value

Type your standard integer (1 to 3,999) or Roman numeral string (I, V, X, L, C, D, M).

3 Review Subtractive Notation Validation

The converter verifies correct standard subtractive notation rules (IV, IX, XL, XC, CD, CM) and flags invalid syntax.

4 Inspect Detailed Breakdown & Copy

Review the additive breakdown equation (e.g. `M (1000) + M (1000) + XX (20) + VI (6) = 2026`) and copy the result with one click.

Frequently Asked Questions

Common questions about using this free online roman numeral converter.

What are the basic Roman numeral symbols and values? ▾
I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1,000.
What is standard subtractive notation in Roman numerals? ▾
Instead of repeating a numeral four times (like `IIII`), a smaller numeral is placed before a larger one to denote subtraction: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, and CM = 900.
Why is the standard maximum Roman numeral 3,999 (MMMCMXCIX)? ▾
In standard classical Roman numerals, the largest basic symbol is M (1,000) and consecutive symbols cannot repeat more than three times. For numbers 4,000 and above, the Vinculum system (a horizontal overline multiplying by 1,000) was used.
Does the Roman numeral system have a symbol for zero? ▾
No. Classical Roman numerals had no zero symbol. The concept of zero was introduced into European mathematics later via Hindu-Arabic numerals.

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