The fifth rule - Addition of basic symbols in additive notation in a Roman numeral

Numerals addition rule in additive notation:

  • A numeral placed immediately after another one of a larger or equal value (next to the right of it), is added to the latter. This is called additive notation.
  • This rule outweigh the third rule, that of subtraction in subtractive notation when writing Roman numerals.
  • Only when a number can't be built by following the addition rule in additive notation, the subtractive notation applies.
  • Also remember the rule no. 2, of repetition (numerals may not occur more than three times in a row in any numeral).


  • Number two (2) is written using a single symbol listed under the first rule: I (1). Placing the I symbol after another I leads to: II (2);
  • Number three (3) is also written by placing I after I (1) twice, so we get: III (3);
  • Number six (6) is written by placing I (1) after V (5), so we get: VI (6);
  • Number seven (7) is written by placing I (1) after V (5) twice, so we get: VII (7);
  • Number eight (8) is written by placing I (1) after V (5) three times: VIII (8) - not IIX;
  • Number eleven (11) is written by adding I (1) to X (10), by placing I (1) after X (10): 11 = 10 + 1 = X + I = XI;
  • Number twenty (20) is written by placing X (10) after another X (10): 20 = 10 + 10 = X + X = XX;
  • Number one hundred four (104) is written by placing IV (4) after C (100), to get 104 = 100 + 4 = C + IV = CIV.

Roman numerals reading rules, summary:

I. The first rule - Roman numerals set of basic symbols

II. The second rule - numerals repetition

III. The third rule - numerals subtraction (subtractive notation)

IV. The fourth rule - what numerals are allowed to be subtracted from larger value numerals in the subtractive notation

V. The fifth rule - numerals addition (additive notation)

VI. The sixth rule - Arabic numbers decomposing (breaking down) into place value subgroups, in expanded notation, before converting to Roman numerals

Examples of converting Arabic numbers into Roman numerals

Roman numerals from 1 to 100

Roman numerals from 1 to 1000