Deciphering Roman Numerals: What They Are and Where to Find Them

On New Year’s Eve, I noticed Roman numerals on Google's homepage in its name: ”GMMXLe.” At that moment, I realized I did not know how to read big Roman numerals. I decided to find out.

The Romans used numbers just as we do. However, whereas we use the Arabic numerals (that is, numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9), the Romans used Roman numerals. However, unlike our system, Roman numerals do not include zero.

Roman numerals appeared in many different places. However, these numbers can still be found today. Some places where you can find Roman numerals are:

• After the names of rulers (e.g., Henry VIII)
• After a historical event (e.g., World War II)
• On clock faces
• Dates in older books
• On outlines, using capital Roman numerals: I, II, III, IV, V; lowercase numerals: i, ii, iii, iv, v; or a combination of both

When trying to figure out a Roman numeral, pretend you are deciphering a code. I studied math in university and realized then that math is a language just like any other, complete with symbols and rules. So, let’s begin with the meaning of the Roman numeral symbols. Quite simply,

• I means 1
• V means 5
• X means 10
• L means 50
• C means 100 (think “C” as in “Cent,” “Century,” “Centennial”)
• D means 500
• M means 1000

The number system we most commonly use, the Arabic system, focuses on addition. For example, the number 25 is 20 + 5. It has even been referred to as five-and-twenty, again emphasizing the addition in our system.

Roman numerals use addition when symbols are arranged from highest to lowest. For example, MMXI means 1000 + 1000 + 10 + 1, or 2011. In this example, M=1000, which is larger than X=10, which is larger than I=1.

However, when working with Roman numerals, you will work with not only addition, but subtraction. When a lower symbol appears before a higher symbol, you need to subtract the lower symbol from the higher symbol. This seems confusing at first, but is actually quite easy.

For example, IV means take one away from 5 (i.e., 5 minus 1). Therefore, IV=4.

Another example, CMV means take 100 away from 1000, then add 5 (i.e., 1000 – 100 + 5) which is 905.

Let’s practice writing some dates:

MCMXLV = 1000 – 100 + 1000 – 10 + 50 + 5 = 1945.

MCMXCIX = 1000 – 100 + 1000 – 10 + 100 – 1 + 10 = 1999.

MMXII= 1000 + 1000 + 10 + 1 + 1 = 2012.

Hopefully, you're a bit more comfortable figuring out Roman numerals. They aren't too hard once you get used to them.