How to Read and Write Roman Numerals
Master the basics in just a few minutes!
The 7 Roman Letters
Roman numerals use just 7 letters. Each one stands for a different number:
The Roman system is built on seven basic symbols. Think of them as the alphabet of Roman numbers - once you know these seven letters and their values, you can read any Roman numeral.
- •There are only 7 symbols - that's it!
- •Each symbol always means the same number
- •The symbols are: I (1), V (5), X (10), L (50), C (100), D (500), M (1000)
- •Notice the pattern: 1, 5, 10, 50, 100, 500, 1000 - they alternate between 1s and 5s
- •You combine these symbols using simple rules to make any number
- •Every Roman numeral you see is just these 7 letters mixed together
Rule 1: Adding Numbers
When a smaller letter comes AFTER a bigger letter, just add them together.
This is how Roman numerals work most of the time. When you see letters going from big to small (left to right), or when a smaller letter comes after a bigger one, you simply add them up.
- +Letters usually go from biggest to smallest, left to right
- +When a smaller letter comes after a bigger one, add them
- +Same letters next to each other get added too (II = 1 + 1 = 2)
- +This is the most common rule - you'll use it all the time
- +Just read from left to right and add as you go
Let's Break Down VI
I comes AFTER V, so we add them: 5 + 1 = 6
Rule 2: Subtracting Numbers
When a smaller letter comes BEFORE a bigger letter, subtract it instead of adding.
This rule has some strict limits to keep things clear. Only three letters (I, X, and C) can be used for subtraction, and each one can only subtract from certain other letters.
- −I can subtract from V and X only (making IV = 4 and IX = 9)
- −X can subtract from L and C only (making XL = 40 and XC = 90)
- −C can subtract from D and M only (making CD = 400 and CM = 900)
- −V, L, and D can never be subtracted - only I, X, and C
- −You can only subtract one letter at a time (not II or XX before another letter)
- −Don't skip values when subtracting (write 99 as XCIX, not IC)
- −There are only 6 valid subtraction combos you need to remember
Let's Break Down IV
I comes BEFORE V, so we subtract: 5 - 1 = 4
Only I, X, and C can subtract - and only from specific letters.
Rule 3: Repeating Letters
You can write the same letter up to 3 times in a row to make bigger numbers.
Repeating letters is a simple way to build numbers. But there are limits - you can only repeat certain letters, and never more than three times.
- ×Only I, X, C, and M can be repeated
- ×You can repeat a letter up to 3 times maximum
- ×Never repeat V, L, or D (they're special middle values)
- ×Instead of VV use X, instead of LL use C, instead of DD use M
- ×When you repeat letters, just add them up (III = 1 + 1 + 1 = 3)
- ×Modern notation avoids four in a row (use IV instead of IIII)
V, L, and D never get repeated. Use X, C, or M instead.
Rule 4: Writing Order
Always write the biggest numbers first, then smaller ones - left to right.
Roman numerals always go from big to small as you read left to right. This makes them easy to read once you know the pattern.
- →Always write from biggest to smallest (left to right)
- →Start with thousands, then hundreds, then tens, then ones
- →Subtraction pairs like IV or IX count as one unit in the order
- →The order applies to the whole number, not the letters inside subtraction pairs
- →Think: thousands → hundreds → tens → ones
- →Never put a bigger number after a smaller one (unless subtracting)
Putting It All Together
This example uses all three rules. Let's break down XLIII step by step:
Rule 2: Subtraction
X comes BEFORE L, so we subtract
Rule 3: Repetition
Same letter repeated 3 times
Rule 1: Addition
Combine the parts together
Breaking Down Complex Numbers
How it works:
How it works:
How it works:
How it works:
Common Mistakes (And How to Fix Them)
Watch out for these easy mistakes!
Quick Tips to Remember
Start with the biggest numbers first and work down
Only I, X, and C can subtract - that's it!
Never repeat V, L, or D - they're special
There are only 6 subtraction combos: IV, IX, XL, XC, CD, CM
When you're not sure, just add - it usually works
Practice with years (like 1999 or 2024) to get better
Try It Yourself!
Can you convert these numbers to Roman numerals?
Ready for More Practice?
Now that you know the rules, try our fun tools to become a Roman numeral pro!