CalcUnit Logo
← Back to BlogOpen Calculator
mathroman numeral

Decoding Antiquity: How to Read Roman Numerals

By CalcUnit History Experts
Decoding Antiquity: How to Read Roman Numerals

Instantly translate complex ancient dates using our Roman Numerals Converter, or read on to master the arithmetic rules of the Roman Empire.

Despite the fall of the Roman Empire over 1,500 years ago, their numbering system is still heavily used today. You see them on the faces of clocks, in the names of monarchs (Queen Elizabeth II), identifying the Super Bowl, and in the copyright dates of movies and television shows.

Unlike our modern Arabic numeral system (0-9) which uses place value (where the position of a '1' tells you if it is ten or a hundred), Roman numerals use a system of addition and subtraction based on seven distinct symbols.

The Seven Core Symbols

The entire system is built on these seven letters from the Latin alphabet:

  • I = 1
  • V = 5
  • X = 10
  • L = 50
  • C = 100
  • D = 500
  • M = 1,000

The Additive Rule

If a smaller or equal symbol is placed after a larger symbol, you simply add the values together.

  • VI = 5 + 1 = 6
  • XX = 10 + 10 = 20
  • MD = 1,000 + 500 = 1,500

You can repeat symbols to add them together, but a strict rule is that you cannot repeat the same symbol more than three times in a row. So, 3 is III, but 4 is NOT IIII.

The Subtractive Rule

To avoid repeating symbols four times, the Romans used subtraction. If a smaller symbol is placed before a larger symbol, you subtract the smaller value from the larger value.

  • IV = 5 - 1 = 4
  • IX = 10 - 1 = 9
  • XL = 50 - 10 = 40
  • CM = 1,000 - 100 = 900

Important Restriction: You can only use I to subtract from V and X. You can only use X to subtract from L and C. You cannot put an I in front of an M to make 999. (999 is correctly written as CMXCIX).

Step-by-Step Translation Example

What year was the movie with the copyright date MCMLXXXIV released? Always break it down into chunks from left to right:

  1. M = 1,000
  2. CM (Smaller before larger) = 900
  3. LXXX (Larger before smaller) = 50 + 10 + 10 + 10 = 80
  4. IV (Smaller before larger) = 4

1000 + 900 + 80 + 4 = 1984.

FAQ

Did the Romans have a symbol for zero? No! The concept of zero as a placeholder did not exist in Roman mathematics. This made complex multiplication and division incredibly difficult for Roman engineers, which is why the world eventually adopted the Arabic numeral system, which includes the zero.

Translate copyright dates and historical texts instantly with the CalcUnit Roman Numerals Converter.

Related Articles