Whats the cap for dodge just wondering.

This really does not help, but I noticed that the dodge stat on your character screen seems to lose its 1:1 interval, because when I play with high dodge I calculate my hero (Jax) to have ~38 dodge when maxed skill (E), yet it displays that I only have a ~33 dodge rating, so maybe after a certain point...lets say around 28-30, its starts losing value...idk...just my observation. My math could be wrong.

No hardcap, but it stacks multiplicatively. Meaning that the higher your dodge is, the lower effect each one has.

The theoretical highest would be:
Katarina with a level 5 Killer Instincts after activating it and Shunpoing (70%)
Dodge Seals + Quintessences (11.25%)
Dodge Mastery (2%)
6 Phantom Dancers (20% each)

So to figure out what your dodge chance is, you take 1-(1-Dodge Chance1)(1-Dodge Chance2)...(1-Dodge ChanceN)

1-(.3)(.8875)(.98)(.80)(.80)(.80)(.80)(.80)(.80)
1-(.068) - 93% dodge chance

QFT.

Really, it has the same effect as it lists, except the numbers don't add, they multiply. Think of it this way, you have runes (11.25%), mastery (2%), ninja tabi (11%), and phantom dancer (20%)

It does:
Did your runes dodge the attack?
if not, then:
Did your masteries dodge the attack?
if not, then:
Did your Tabi dodge the attack?
if not, then:
Did your Phantom Dancer dodge the attack?
if not, then:
You get hit.

For a total chance of:
(1-.1125) * (1-.02) * (1-.11) * (1-.2) = 0.6193 chance to get hit or (1-.6193) =
38.07% chance to dodge.

EnderA got it right

100% but you will never get there. I win