How to Read Roman Numerals

By Molly MaGuire
Roman numerals engraved in a stone wall.
Charles Schultz/iStock/Getty Images

Knowing Roman numerals enables you to read certain clocks and chapter titles, and the year in movie credits, for example. Roman numerals use a numbering technique based on seven letters: I, V, X, L, C, D and M. The symbol I represents a value of 1; V represents 5; X represents 10; L represents 50; C represents 100; D represents 500 and M represents 1000.

Conversion Rules

When the symbol has a greater value than the symbol after it, add the symbols, such as: XI = X + I = 10 + 1 = 11. When the symbol has a lesser value than the symbol after it, subtract the symbol with the lesser value from the symbol with the greater value: IX = X – I = 10 - 1 = 9. When the symbols have equal value, add them: XX = X + X = 10 + 10 = 20.

Roman Numerals to Decimals

To see these rules applied to a larger number, convert MCMLXXXVI to decimal numbers. Starting with "VI," move from right to left and apply the rules. I + V + X + X + X + L + M - C + M. This works out to 1 + 5 + 10 + 10 + 10 + 50 + 1000 – 100 + 1000 = 1986. Another example is DCCLXXXIV. Starting with "IV," move from right to left and apply the rules. V - I + X + X + X + L + C + C + D. This works out to 5 - 1 + 10 + 10 +10 + 50 + 100 + 100 + 500 = 784.

Decimals to Roman Numerals

You can also convert a decimal number to a Roman numeral. Break down the decimal number into 1,000s, 100s, 10s and ones. To convert 2014, break it down to 2000, 10 and 4. Then, convert. So, 2000 = MM; 10 = X; 4 = IV. The year 2014 works out to MMXIV.

About the Author

Molly MaGuire has a Bachelor of Science in computer science and a Master of Science in international relations. She has taught at the university level for more than seven years and has worked as an instructional designer for more than nine years. She enjoys researching and discussing topics such as education, politics and technology.