Probability Distribution for rolling/summing 3 Dice

[Database]

Pulled this off a site, it's helpful to know what your chances are with an unmodified roll:

The highest possible roll is 3 * 6 = 18
The lowest possible roll is 3 * 1 = 6

The results are symmetrical.

P(3) = P(18) = 1/216
P(4) = P(17) = 3/216
P(5) = P(16) = 6/156
P(6) = P(15) = 10/216
P(7) = P(14) = 15/216
P(8 ) = P(13) = 21/216
P(9) = P(12) = 26/216
P(10) = P(11) = 26/216

So most often you will roll 8-13, (146 times out of 216) followed by 7 and 14, etc. So if you have a skill at 13+, you will succeed relatively frequently. Criticals are rare.