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How to Convert Roman Numerals: 3 Easy Methods

Posted by Hannah Muniz | Aug 15, 2019 3:00:00 PM

General Education

 

feature_roman_numerals-1

You’ve likely come across Roman numerals in your everyday life and wondered why we still feel the need to use them today. After all, isn't there a much easier way to write out numbers?

In this article, we’ll explain how Roman numerals work and provide you with several Roman numerals converter charts, which you can use to learn and review this ancient numerical system. We’ll also give you three methods you can use for remembering Roman numerals.

 

What Are Roman Numerals and How Do They Work?

Roman numerals are an ancient numbering system that originated in Rome (hence the name "Roman"). As you probably know, they're very different from what the majority of people and cultures use today, which are Arabic numerals, or the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.

Unlike Arabic numerals, Roman numerals are a tight system of only seven symbols, which you can combine to form new numbers through special rules of addition and subtraction (we'll explain how these rules work in just a moment).

Here are the seven Roman numerals and what they mean:

Roman Numeral I V X L C D M
Arabic Numeral 1 5 10 50 100 500 1,000

 

These are the fundamental numbers Roman numerals represent when used alone.

To form other numbers using this system, you place the numerals side by side to indicate addition. If a numeral comes after a numeral that is larger or equal in value, then it must be added to the numeral before it.

For example, if you wanted to write 3 in Roman numerals, you’d simply write I three times like this: III. This means I + I + I (or 1 + 1 + 1).

Or, let’s say you wanted to write the number 56 in Roman numerals. To do this, you'd start with the largest unit represented by a Roman numeralin this case, that’s 50, which is represented by an L. Then, you’d add a V (5) followed by an I (1) to make 6. This would give you LVI, or 56.

 

body_roman_numerals_ring

 

The big rule to remember is that you can’t add more than three of the same Roman numeral together. This is where subtraction comes into play. A smaller numeral placed before a larger numeral indicates subtraction of that smaller numeral from the larger one.

For example, to make the number 4, you can't just write IIII because you can’t add more than three I’s together. What you’ll need to do is subtract 1 from 5 (I from V). To depict subtraction in Roman numerals, you must put the smaller numeral directly before the numeral it’s being subtracted from. For 4, this would be IV (meaning V I, or 5 − 1).

Note that you can’t subtract more than one value from a Roman numeral.

Here’s another example: say you want to write the number 719 in Roman numerals. To start, you’d have to find the biggest valuethat’s the hundreds. Remember that D stands for 500 and C stands for 100, so you can simply add these symbols together to form 700: DCC.

Now, we need to get 19. If you add 10 (X) and 5 (V) together, you’ll get 15. But you can’t add four I’s after that to get 19, as that would be more than three of the same numeral. Instead, you can use two X’s and subtract I from the second X. This would make XIX. Literally, this means X + (X I), or 10 + (10 1), which, as we know, equals 19.

Now, put these two parts together to get the Roman numeral combination for 719: DCCXIX.

Subtraction is only used for specific numbers and number combinations. These are any numbers that end with the digits 4 or 9, as well as the numbers 40, 90, 400, and 900:

Correct Roman Numeral (Using Subtraction)

INCORRECT Roman Numeral (Using Addition)

Meaning

IV

IIII*

4

IX

VIIII

9

XL

XXXX

40

XC

LXXXX

90

CD

CCCC

400

CM

DCCCC

900

*Though normally considered incorrect usage, IIII is sometimes used instead of IV on clocks.

As you probably noticed above, Roman numerals only go up to M (1,000). According to the rules of addition and subtraction, this means that the biggest number we can form in Roman numerals is MMMCMXCIX, or 3,999.

But there are ways you can represent numbers even higher than this.

One method is to draw a horizontal line, or bar, across a Roman numeral (or combination of numerals) to multiply it by 1,000. For example, if you wanted to write 5,000, you’d write V.

Another less common way of writing even larger numbers involves placing a border or box that’s open at the bottom around a Roman numeral to multiply it by 100,000. So I with a box around it means 100,000, whereas IV with a box around it means 400,000.

 

body_roman_numeral_clock

 

Why Should You Know What Roman Numerals Are?

Roman numerals are still used today in a variety of situations, so it’s vital that you understand how to read them.

Here are three prime examples of times you’ll see Roman numerals being used:

  • Movie release dates: Release years of movies typically appear in Roman numerals at the end of credits and on the backs of DVD and Blu-ray cases.

Although Arabic numerals far outnumber (pun intended) Roman numerals in terms of the breadth of situations in which they’re used, it’s certainly worth taking some time to sit down and learn how to use Roman numerals—especially if you plan to go into football or film production!

 

Roman Numerals Converter Charts

This Roman numeral converter chart shows all the major Roman numerals written out:

Roman Numeral

Meaning

Roman Numeral

Meaning

I

1

LX

60

II

2

LXX

70

III

3

LXXX

80

IV

4

XC

90

V

5

C

100

VI

6

CC

200

VII

7

CCC

300

VIII

8

CD

400

IX

9

D

500

X

10

DC

600

XX

20

DCC

700

XXX

30

DCCC

800

XL

40

CM

900

L

50

M

1,000

 

These are the main numbers you can write using the seven Roman numerals.

But if you want to write even bigger numbers, here is the Roman numerals converter chart to use. Recall that a bar on top multiplies the number by 1,000.

Roman Numeral

Meaning

M or I

1,000

MM or II

2,000

MMM or III

3,000

IV

4,000

V

5,000

X

10,000

L

50,000

C

100,000

D

500,000

M

1,000,000

 

 

body_roman_numeral_year_buildingCORNERSTONES of NY/Flickr

 

A lot of people are curious about how years look when rendered in Roman numerals, as this is a common practice used on buildings (usually to indicate the date of construction), in movies, and to emphasize birthdays and other important dates on things such as rings and tattoos.

Below is a Roman numeral date converter chart you can use to help you quickly get a feel for what different years look like in Roman numerals:

Roman Numeral

Year

MCM

1900

MCMX

1910

MCMXX

1920

MCMXXX

1930

MCMXL

1940

MCML

1950

MCMLX

1960

MCMLXX

1970

MCMLXXX

1980

MCMXC

1990

MM

2000

MMX

2010

MMXX

2020

 

 

How to Remember Roman Numerals: 3 Methods

You won’t always have access to Roman numeral converter charts like the ones we’ve given you above, so how can you make sure you understand how to correctly read Roman numerals?

Here are three methods you can use to help you remember Roman numerals and how they work.

 

#1: Memorize a Mnemonic Device

Lots of students find it easiest to memorize the seven Roman numerals by using a simple mnemonic device. Such a device can help you remember the Roman numerals by reminding you of the letters used to represent them from smallest to largest, or vice versa.

Once again, these letters are as follows:

  • I (1)
  • V (5)
  • X (10)
  • L (50)
  • C (100)
  • D (500)
  • M (1,000)
Here are some common mnemonic devices:
  • My Dear Cat Loves Xtra Vitamins Intensely (Source)
  • I Value Xylophones Like Cows Dig Milk (Source)
  • I Value Xylophones Like Cows Do Milk (Source)
  • MeDiCaL XaVIer (Source)

Feel free to make your own mnemonic device instead if you don’t like any of these or find them difficult to memorize.

 

#2: Come Up With Your Own Associations

Some people prefer to memorize Roman numerals by coming up with specific associations with the letters and numbers they represent or by thinking of certain words/phrases (not necessarily mnemonic devices).

For example, one popular trick is to think of the Roman numeral M (which means 1,000) as standing for "Millennium," and the Roman numeral C (which means 100) as standing for "Century."

Other people think in terms of word associations or acronyms. For example, the Roman numerals L, C, and D might remind you of an LCD computer monitor. Knowing this association can help you remember the correct (ascending) order of these numerals.

Try finding your own associations to help you remember Roman numerals.

 

body_pointer_finger_roman_numeral

 

#3: Use the Hand Trick

The last way to help you remember Roman numerals is to use what's commonly called the hand trick, which can be used for memorizing the first three Roman numerals (I, V, and X).

Start by putting up just one of your fingers to make a figure that looks like the Roman numeral I. So one finger = I. Simple enough, right?

Now, make a V-shape with one hand by pushing your thumb away from your other four fingers. Five fingers in a V-shape should remind you that the Roman numeral V equals 5.

Finally, make an X with both your hands. Doing this should make you see that 10 fingers in an X-shape corresponds to the Roman numeral X, or 10.

 

Review: Roman Numerals Converter Quiz

Before we wrap up this article, let’s take a short Roman numeral converter quiz to see how well you’ve managed to memorize Roman numerals and how they work (answers below).

 

Write the following numbers in Roman numerals:

  1. 49
  2. 426
  3. 2,999
  4. 50,000
  5. Your birth year

 

Answers:

  1. XLIX
  2. CDXXVI
  3. MMCMXCIX
  4. L
  5. Answer varies depending on the year you were born

Here’s a brief Roman numeral birthday converter chart you can use as a reference:

Year

Roman Numeral

Year

Roman Numeral

2019

MMXIX

2004

MMIV

2018

MMXVIII

2003

MMIII

2017

MMXVII

2002

MMII

2016

MMXVI

2001

MMI

2015

MMXV

2000

MM

2014

MMXIV

1999

MCMXCIX

2013

MMXIII

1998

MCMXCVIII

2012

MMXII

1997

MCMXCVII

2011

MMXI

1996

MCMXCVI

2010

MMX

1995

MCMXCV

2009

MMIX

1994

MCMXCIV

2008

MMVIII

1993

MCMXCIII

2007

MMVII

1992

MCMXCII

2006

MMVI

1991

MCMXCI

2005

MMV

1990

MCMXC

 

 

body_super_bowl_roman_numeralsAustin Kirk/Flickr

 

Final Words: Why You Should Learn Roman Numerals

Though Roman numerals originated in ancient Rome and aren’t used much in everyday life today, they’re still important to know, especially if you want to be able to read old-fashioned analog clocks and years for things like movie releases.

The Roman numeral system is based on seven essential numerals: I, V, X, L, C, D, and M (1, 5, 10, 50, 100, 500, and 1,000, respectively). Roman numerals are written from left to right starting with the biggest unit.

Numerals can be added together to form new numbers (e.g., III = I + I + I = 3), but no more than three of the same numeral can be added together.

In addition, to form any numbers ending with 4 or 9 or the numbers 40, 90, 400, and 900, you must subtract from the larger unit because you cannot add more than three of the same numeral. For example, IV = V I = 5 1 = 4.

To represent a very large number (1,000+), add a horizontal bar above the numeral to multiply it by 1,000. So X = 10 * 1,000 = 10,000.

There are many ways you can help yourself remember Roman numerals. Here are three methods:

  • Memorize a mnemonic device
  • Come up with your own associations
  • Use the hand trick

You should now know everything there is to know about Roman numerals!

 

What’s Next?

There's a lot more to numbers than Roman numerals. Take a look at our expert guides to learn how to round numbers with decimals in them (coming soon), how to convert decimals to fractions, and how to add and subtract fractions.

Interested in learning about large numbers? We explain what comes after a trillion and give you the names of tons of big numbers. We also go over how many zeros are in a million, a billion, and a trillion.

Have friends who also need help with test prep? Share this article!
Hannah Muniz
About the Author

Hannah received her MA in Japanese Studies from the University of Michigan and holds a bachelor's degree from the University of Southern California. From 2013 to 2015, she taught English in Japan via the JET Program. She is passionate about education, writing, and travel.



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