1900
MCM
3 letters
1900 in Roman numerals — MCM
The year 1900 is MCM in Roman numerals — M=1000, CM=900 added together, 3 letters in all.
M
1000
CM
900
- Roman numeral
- MCM
- Broken up
- M=1000 + CM=900
- By place value
- 1000 = M · 900 = CM
- Letters
- 3 letters
- Subtractive pairs
- Used — CM
Why IV and not IIII
Because the same letter is never repeated four times. Six pairs put a smaller letter first so it is subtracted: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
Nearby years
Seven letters and six subtractive pairs
These thirteen rows are the whole system. Subtract the largest value you can, over and over, and any year falls out.
M
1000
CM
900
D
500
CD
400
C
100
XC
90
L
50
XL
40
X
10
IX
9
V
5
IV
4
I
1
Decade by decade
1900s
1910s
1920s
1930s
1940s
1950s
1960s
1970s
1980s
1990s
2000s
2010s
2020s
2030s
2040s
2050s
2060s
2070s
2080s
2090s
2100s
How to read this
- Add from the left, but subtract when a smaller letter comes before a larger one.
- There are only seven letters: M=1000, D=500, C=100, L=50, X=10, V=5, I=1.
- The same letter repeats at most three times — the fourth becomes a subtractive pair.
- There is no zero, and the largest place value is always written first.
Frequently asked questions
Q. How do you write 1900 in Roman numerals?
MCM — that is M (1000) + CM (900) written in a row.
Q. How many letters is MCM?
3.
Q. Does it use a subtractive pair?
Yes: CM=900.
Q. What about the years either side?
1901 is MCMI.