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Learn Roman Numerals for School

Practice converting between Roman numerals and decimal numbers for history, math, and classical studies.

Nid oes angen mewngofnodi
Roman numeral
MMXXIV

Common values

Roman numeral rules: I=1, V=5, X=10, L=50, C=100, D=500, M=1000.

Subtractive notation: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Standard numerals max out at MMMCMXCIX (3999).

Vinculum: a bar over a numeral multiplies it by 1000 (VΜ… = 5000, XΜ… = 10000, MΜ… = 1,000,000), extending the range to 3,999,999.

Education tips

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Use the preset buttons to explore tricky conversions: 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD), 900 (CM) β€” these are the subtractive notation cases.

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Subtractive notation rule: when a smaller symbol precedes a larger one, subtract it. IV = 5βˆ’1 = 4. XL = 50βˆ’10 = 40. CM = 1000βˆ’100 = 900.

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Romans didn't have zero or negative numbers. The system only goes from 1 to 3999. Numbers beyond 3999 required special notation not in standard use.

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Test yourself: convert 1999 before checking. It's MCMXCIX (M=1000, CM=900, XC=90, IX=9). Complicated but follows the rules!

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