Roman Numeral Calculator Convert between decimal numbers and Roman numerals (1โ3999) with a reference chart.
Roman Numeral Calculator
Convert between decimal numbers and Roman numerals (1โ3999) with a reference chart.
Choose Direction
Select Number โ Roman or Roman โ Number conversion.
Enter Value
Type a decimal number (1-3999) or a Roman numeral.
View Result
See the converted value with a reference chart of all Roman symbols.
What Is Roman Numeral Calculator?
The Roman Numeral Calculator converts between standard decimal numbers and Roman numerals in both directions. Enter a number (1 to 3999) to see its Roman numeral representation, or enter a Roman numeral (like MMXXVI) to find its decimal value. The calculator validates inputs and includes a complete reference chart showing all Roman numeral symbols and their subtractive forms (IV, IX, XL, XC, CD, CM). The traditional Roman numeral system cannot represent zero or numbers above 3999.
Why Use Roman Numeral Calculator?
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Bidirectional conversion: numbers โ Roman numerals
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Input validation for both number ranges and Roman numeral syntax
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Complete reference chart for all symbols and subtractive forms
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Supports the full range 1 to 3999 (I to MMMCMXCIX)
Common Use Cases
Education
Learn and practice Roman numeral conversions for school.
Document Formatting
Convert chapter numbers, outline items, or dates to Roman numerals.
Clock Reading
Decode Roman numeral clock faces.
Historical Dates
Convert years in historical inscriptions and monuments.
Technical Guide
Conversion from decimal uses a greedy algorithm with the value-symbol pairs: (1000,M), (900,CM), (500,D), (400,CD), (100,C), (90,XC), (50,L), (40,XL), (10,X), (9,IX), (5,V), (4,IV), (1,I). For each pair, repeatedly subtract the value and append the symbol while the remaining number is โฅ the value. Conversion from Roman to decimal scans left to right: if the current symbol's value is less than the next symbol's value, subtract it (subtractive notation: IV = 5-1 = 4); otherwise, add it. Valid subtractive pairs are: IV(4), IX(9), XL(40), XC(90), CD(400), CM(900).
Tips & Best Practices
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1Roman numerals have no symbol for zero โ the concept of zero came later
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2The maximum standard Roman numeral is 3999 (MMMCMXCIX)
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3Subtractive notation is used for 4s and 9s: IV, IX, XL, XC, CD, CM
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4Modern use of Roman numerals includes Super Bowl numbers, movie sequels, and clock faces
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๐ข Math & CalculatorsFrequently Asked Questions
Q Why can't Roman numerals go above 3999?
Q Is there a Roman numeral for zero?
Q What year is MMXXVI?
Q Why is 4 written as IV instead of IIII?
Q Are lowercase roman numerals valid?
About This Tool
Roman Numeral Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser โ your data never leaves your device. No registration or installation required.