Roman Numeral Converter
Convert numbers from 1 to 3999 into Roman numerals or turn Roman numerals back into Arabic numbers. Invalid notations are detected and flagged.
Result
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Reference table
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
How do Roman numerals work?
Roman numerals use letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Smaller values before larger ones are subtracted (IV=4, IX=9). Numbers are read left to right.
What is the largest number in Roman numerals?
Standard Roman numerals go up to 3,999 (MMMCMXCIX). Larger numbers use a vinculum (bar above) to multiply by 1,000, but this is rarely needed in modern usage.
Why does the calculator reject IIII or IC as invalid?
The calculator only accepts today's standard notation: it converts your input and checks whether converting it back produces exactly the same characters. Subtraction is only allowed for I before V and X, X before L and C, and C before D and M, and no symbol appears more than three times in a row. That is why 4 = IV (not IIII as on some clocks), 99 = XCIX (not IC) and 1999 = MCMXCIX (not MIM).
Guide
What is the Roman Numeral Converter?
The Roman numerals calculator converts Arabic numbers into Roman numeral notation and vice versa.
How does the Roman Numeral Converter work?
Enter an Arabic number (1-3,999) or Roman numerals. The calculator converts to the other form. The subtractive rule (e.g. IV = 4) is correctly applied.
Key Data and Facts
Basic symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1,000. Subtractive rule: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Max. standard notation: 3,999 (MMMCMXCIX).
Step-by-Step Guide
How to use the Roman numeral calculator step by step: 1. Choose the input direction – Arabic to Roman or Roman to Arabic. 2. Enter the number – for Arabic numbers, enter a value between 1 and 3,999. For Roman numerals, enter the characters I, V, X, L, C, D, M. 3. Read the result – the calculator displays the converted number immediately. 4. Understand the subtraction rule: a smaller character placed before a larger one is subtracted. IV = 5 - 1 = 4, IX = 10 - 1 = 9, XL = 50 - 10 = 40, XC = 100 - 10 = 90. 5. Addition rule: identical or descending characters are added. VIII = 5 + 1 + 1 + 1 = 8. A maximum of three identical characters in a row (III = 3, but 4 = IV, not IIII). Typical uses: years on buildings (MMXXVI = 2026), chapter and section numbering, clock faces. Tip: break large numbers down from left to right into thousands, hundreds, tens and units.
Calculation Example
Arabic 1994 to Roman: 1000=M, 900=CM, 90=XC, 4=IV — result: MCMXCIV. Roman CDLXVII to Arabic: 400+50+10+5+1+1 = 467.
Sources
Official sources
Calculations are based on applicable German laws and official data:
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
Mathematics
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