How to Denote 4 and 9 in Roman Numerals

The numbers 4 and 9 are some of the most complicated in Roman Numerals because they don't follow the same pattern as 1 through 3 or 6 through 8. Once you know the trick, it's easy!

Steps

  1. 1
    Know your basic Roman Numeral symbols. I=1, V=5, X=10, L=50, C=100, D=500, M=1000
    • For these symbols, I, X, C, M, they can only be repeated a maximum of three times only.
    • Example: III, XXX, CCC, MMM
    • There is no VVV, LLL and DDD
  2. 2
    Learn the basic structure for repeated symbols (which doesn't work for 4 and 9). If you put something after V, X, L, C, D, M, that means to add the values together. Remember that any symbol can only be repeated three times.
    • I=1
    • II=1+1
    • III=1+1+1
    • IIII...I+1+1+1+1...Nope!
    • VI=5+1
    • VII=5+1+1
    • VIII=5+1+1+1 (symbol repeated three times max)
    • VIIII=5+1+1+1+1...Nope!
    • XI=10+1
    • XII=10+1+1
    • XIII=10+1+1+1
    • XIIII=10+1+1+1+1...Nope!
    • LI=50+1
    • LII=50+1+1
    • LIII=50+1+1+1 (symbol repeated three times max)
    • LIIII=L+1+1+1+1...Nope!
    • CI=100+1
    • CII=100+1+1
    • CIII=100+1+1+1
    • CIIII=C+1+1+1+1...Nope!
    • DI=500+1
    • DII=500+1+1
    • DIII=500+1+1+1 (symbol repeated three times max)
    • DIIII=D+1+1+1+1...Nope!
    • MI=M+1
    • MII=M+1+1
    • MIII=M+1+1+1
    • MIIII=M+1+1+1+1...Nope!
  3. 3
    For Roman numerals that end in 4 or 9, you need to put an I before V, L, C, D, M, X. This means "to subtract" instead of "to add." For this lesson, we are learning only "V" and "X". Remember that any symbol can only be repeated three times.
    • Then, what about 4? Is it IIII? No. Since V = 5, you put "I" before "V" to get the value of 4. So, it becomes,
      • IV=5-1=4
      • XIV =10+4=14
      • XXIV=20+4=24
      • XXXIV=30+4=34
    • Then, what about 9? Is it VIIII? No. Since X = 10, you put "I" before "X" to get the value of 9. So, it becomes,
      • IX =10-1=9
      • XIX=10+9=19
      • XXIX=20+9=29
      • XXXIX=30+9=39

Tips

  • Also note that there are no zero's (0's) in the Roman Numeral system.

Article Info

Categories: Mathematics