# 10 Roman Numerals

Sometimes we’ll see roman numerals on compounding formulas and prescriptions or even on sig codes / pharmacy abbreviations (click here to see these sig codes.)

# How To Interpret & Write Roman Numerals

1. Start from left to right.
2. When a larger roman numeral comes after a smaller one, subtract them.
3. Subtracting more than one pair of numeralsis not allowed.
4. V L and D can not be subtracted from larger numerals.
5. I can only be subtracted from V or X.
6. X can only be subtracted from L or C.
7. C can only be subtracted from D or M.
8. Perform all relevant subtractions first before adding.
9. Add up to 3 identical numerals together when repeated.
10. V L and D are never repeated.
11. When a smaller roman numeral comes after a larger one add them together. Let’s look at some examples:

DCCLXXVII = 777

MMXIV = 2014

CCL = 250

CXXV = 125

XXIII = 23

DLX = 560

MCCXXII = 1222

XIX = 19

Try converting the following:

CXXIII

808

MCMLXXXV

143

CMXI

1776

MMXX

1234