Learn how to convert large numbers to Roman numerals

The Romans created the numeral system so that the largest letter used is M (1000). This meant that no more than 3 consecutive M’s (3000) could be used, meaning the largest possible Roman numeral combination was 3999 (MMMCMXCIX).

This limited scope for creating numbers greater than 3999. So the Romans devised a system of adding a line above the existing numerals. This line means the numeral is multiplied by 1000, making it possible to create millions of different number combinations.

The following table explains this large number rule.

Normal NumeralsOver-line Numerals

In essence, if you wish to convert a number that is equal to, or greater than 4,000, you:

Firstly: remove the last 3-digits and convert them to numerals. Unless they are ‘000’, in which case you discard them and continue, since there is no numeral that represents zero.

Secondly: convert the remaining digits, and add a line above them.

Lastly: join the numerals together ensuring the numerals with the lines above are at the beginning.

Example: Lets say you wanted to write 15,606 as Roman numerals, this is the process we use to do the conversion:

  1. Separate the hundreds, tens and ones (606) from the number 15,606.
  2. Convert 606 to Roman numerals = DCVI (‘DC+V+I’ = ‘600+5+1’).
  3. Convert 15 to Roman numerals = XV (‘X+V’ = ‘10+5’).
  4. Multiply XV by 1,000 = XV.
  5. Join the two converted results together: ‘XV’ and ‘DCVI.’

Answer = XVDCVI