Roman numerals | The National Archives: "Examples:
I or j = 1
II or ij = 2 (1+1)
III or iij = 3 (1+1+1)
IIII or iiij or IV = 4 (1+1+1+1) or (5-1)
V =5
VI or vj =6
VII or vij = 7 (5+1+1)
VIII or viij = 8 (5+1+1+1)
IX or Viiij = 9 (10-1) or (5+1+1+1+1)
X = 10
XI or xj = 11 (10+1)
XIX = 19 (10+(10-1))
XX = 20 (10+10)
XXX = 30 (10+10+10)
XXXX or XL = 40 (10+10+10+10) or (50-10)
L = 50
LX = 60 (50+10)
LXX = 70 (50+10+10)
LXXX or iiijxx = 80 (50+10+10+10) or (4x20)
LXXXX or XC = 90 (50+10+10+10+10) or (100-10)
XCIX or iiijxxxix = 99 ((100-10)+(10-1)) or ((4x20)+10+(10-1))
C = 100
CI or cj = 101 (100+1)
CC = 200 (100+100)
CCC = 300 (100+100+100)
CCCC or iiijc = 400 (100+100+100+100) or (4x100)
D = 500
DC = 600 (500+100)
M = 1000
MDCCCCLXXXV or MCMLXXXV = 1985 (1000+500+100+100+100+100+50+10+10+10+5) or (1000+(1000-100)+50+10+10+10+5)
But
Ml = 1000 (mille)
MM or MlMl = 2000 (1000+1000) (mille+mille)"
