Roman numerals date back as far as 800 B.C. They combine seven basic letters to create small and large numbers. Keep reading to learn how to convert Roman numerals to everyday numbers, the history of Roman numerals, and where you might see them today.
When combined in various forms, these seven letters create new numbers. Their placement is important, as the same letters create an entirely new number when in a different order. Here they are, from smallest to largest:
You can use a Roman numerals chart or conversion table to look up Roman numerals. Alternatively, you can easily learn how to calculate them yourself with a few simple rules.
Familiarize yourself with Roman numerals using these examples. If you commit as many of them to memory as possible, you'll immediately recognize how they stack up and can be used to represent any kind of number.
I = 1
XX = 20
CL = 150
II = 2
XXI = 21
CC = 200
III = 3
XXII = 22
CCC = 300
IV = 4
XXIII = 23
CD = 400
V = 5
XXIV = 24
D = 500
VI = 6
XXV = 25
DC = 600
VII = 7
XXVI = 26
DCC = 700
VIII = 8
XXVII = 27
DCCC = 800
IX = 9
XXVIII = 28
CM = 900
X = 10
XXIX = 29
M = 1000
XI = 11
XXX = 30
MI = 1001
XII = 12
XL = 40
MV = 1005
XIII = 13
L = 50
ML = 1050
XIV = 14
LX = 60
MD = 1500
XV = 15
LXX = 70
MCM = 1900
XVI = 16
LXXX = 80
MCMXCIX = 1999
XVII = 17
XC = 90
MM = 2000
XVIII = 18
C = 100
MMD = 2500
XIX = 19
CI = 101
MMM = 3000
The position of the letters I, V, X, L, C, and D is what determines the value of the actual Roman numeral. An I in the wrong place can be the difference between 9 and 11, or even 99 and 101.
More rules for understanding Roman numbers include:
If smaller numbers follow larger numbers, add the numbers.
For example: In the Roman numeral XII, you add 10, 1, and 1, which makes 12.
If a smaller number precedes a larger number, subtract the smaller number.
For example: In the Roman numeral IV, you subtract calls 1 from 5, which makes 4.
Roman numerals don't use four identical letters in a row.
For example: You'd never exceed XXX, or 10+10+10, for the tens placement. Since we can't use four identical numerals in a row, 40 would not be XXXX but, rather, XL.
Any time you see a line, that indicates the number should be multiplied by a thousand.
For example: When V looks like V̅, that indicates 5 x 1000 = 5000.
- Remember to treat each part of the number separately (ones, tens, hundreds, etc.).
For example: Even though 1999 is one fewer than 2000, you write MCMXCIX instead of MIM because you can’t skip place value.
You can use either capital or lowercase letters to write Roman numerals.
For example: XVI and xvi both mean 16.
As you add more numbers, the math gets more and more important, but not much more complicated. Read on to learn more about translating Roman numbers.
In order to break down a longer number like MCMLXXXIV into parts, consider this:
- M is for the thousands (1000).
- CM is for the hundreds (1000-100 = 900).
- LXXX is for the tens, consisting of an L for 50 and XXX for 30 (10+10+10), adding up to 80.
- IV is for the ones (5 - 1 = 4).
This gives us 1000 + 900 + 80 + 4, or 1984.
Let's see a few more examples of large numbers, as would be the case when representing a year:
- MCMXCIV = 1994
Watch how we advanced from 1984 to 1994. The LXXX (80) became XC (90). So, now we have M for 1000, CM for 100, XC for 90 (100 minus 10), and IV for 4.
- MDCCLXXVI = 1776
Here, we have M for 1000, D for 500, CC for 200, L for 50, XX for 20, V for 5, and I for 1. Add those all up and you have 1776.
- MCDXCII = 1492
We can discern that breaking it down: M = 1,000; CD = 400 (500 - 100); XC = 90 (100 - 10); and II = 2 (1 +1).
- MMX = 2010.
MMX is short and sweet: M = 1,000, M = 1,000, and X = 10. That's 2010!
Historians believe that Roman numerals originated between 900 and 800 B.C. in ancient Rome.
The symbol for 1 in the Roman numbering system represents a single tally mark. People would notch I into wood or dirt to keep track of items or events they were counting.
But things soon became complicated when they counted by ones alone. What happens after 10? Or 100? The answer is in your fingers!
The Roman numeral for 1 is a single line, just like one finger. The Roman number for 5 is V for the V-shape between the thumb and the index finger when all five of our fingers are spread. If you hold up ten fingers, you’ll find an X when the two Vs merge at the tips of our index fingers – which is why X represents 10.
So why learn about Roman numerals now in the 21st century? Believe it or not, Roman numerals are still used today in a variety of applications. For example:
- In outlines for a story or report
- On clocks and watch faces, such as IV for the number 4
- In books to number prefaces, forewords, and chapters
- On films and big events, such as Rocky II and Super Bowl XLVI
- For monarchs, such as Elizabeth II and Felipe VI
- For Roman Catholic popes, such as Pope John Paul II and Pope Benedict XVI
Understanding how to read and write Roman numerals is an important math skill. It requires adding and subtracting, and is a great way to practice place value skills. For more practice on writing out numbers in different contexts, check out a helpful article on writing numbers.