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.
Roman Numerals Chart

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

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