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Roman Numerals


Roman numerals consist of seven symbols:
  • I = 1
  • V = 5
  • X = 10
  • L = 50
  • C = 100
  • D = 500
  • M = 1000
The Roman numeral system did not have a symbol to represent zero.  The value of a Roman numeral equals the sum of the value symbol values within the numeral. Examples include:
  • XXXIII = 33 (= 10 + 10 + 10 + 1 + 1 + 1)
  • CLVII = 157 (= 100 + 50 + 5 + 1 + 1)
  • MMCXII = 2112 (= 1000 + 1000 + + 100 + 10 + 1 + 1)
Roman numerals from 1 through 20 are listed below:

1 = I 11 = XI
2 = II 12 = XII
3 = III 13 = XIII
4 = IV 14 = XIV
5 = V 15 = XV
6 = VI 16 = XVI
7 = VII     17 = XVII
8 = VIII     18 = XVIII
9 = IX 19 = XIX
10 = X 20 = XX


Upon reviewing the entries within the table above, it may be noticed that:
  • No symbol appears more than three times consecutively as the Romans used the following to represent numbers such as 4, 9, 40, 90:
    • When a symbol of lesser value is written in front of a symbol of greater value, the smaller number is subtracted from the larger number
      • Examples Include:
        • IV = 4 (= 5 − 1)
        • IX = 9 (= 10 − 1)
        • XL = 40 (= 50 − 10)
        • XC = 90 (= 100 − 10)
Example #1:
Express the number 999 in Roman numerals


Solution #1:
The number 999 equates to 900 + 90 + 9

For 900, we use  1000 − 100: CM
For 90, we use 100 − 10: XC
For 9, we use 10 − 1: IX

Therefore, 999 may be written as: CMXCIX


Example #2:
Express the number 2792 in Roman numerals


Solution #2:
The number 2792 equates to 2000 + 700 + 90 + 2

For 2000, we use two M's: MM
For 700, we use 500 + 100 + 100: DCC
For 90, we use 100 − 10: XC
For 2, we use 1 + 1: II

Therefore, 2792 may be written as: MMDCCXCII