At level 100, 4 EVs = 1 point in that stat. For the other levels you get that proportion of the stats, so if you had full EVs at level 50 that's 63 points at level 100 or about 31 at level 50.
So for the levels you chose, the approximate EVs for 1 point are:
Level 5 = 80
Level 25 = 16
Level 40 = 10
level 50 = 8
level 75 = 6
level 100 = 4