Calculating "advantage" when trying to hit with both dice

[Madeiner]

Hello,

i'm trying out some houserule for 5e, in which sometimes you can get a crit if you hit the enemy AC with both dice when you have advantage. Can anyone help me calculate the chances of a critical hit in this case?

[OldTrees1]

So 3 cases (p = probability to hit on a normal roll):
0 rolls hit: Miss : (1-p)^2
1-2 roll hits: Hit : 2p(1-p)
2 rolls hit: Hit and also Crit : p^2

Old chance to Hit with Advantage = the new chance to Hit.
Old chance to Hit with Disadvantage = the new chance to not only Hit (included above) but also Crit.
Old chance to Hit with Advantage - Old chance to Hit with Disadvantage = the new chance to Hit but not Crit.

[Madeiner]

Thank you :) Quick and effective!

[Eric Diaz]

Yeah, it is identical to disadvantage. Here are the chances if you need them (can't paste the table for some reason, if anyone can do it feel free to do so...):

http://methodsetmadness.blogspot.com.br/2016/11/d-5e-advantagedisadvantage-converted-to.html

[Blood of Gaea]

Yeah, it is identical to disadvantage. Here are the chances if you need them (can't paste the table for some reason, if anyone can do it feel free to do so...):

http://methodsetmadness.blogspot.com.br/2016/11/d-5e-advantagedisadvantage-converted-to.html
https://i.imgur.com/DXG5NHA.jpg

[Eric Diaz]

...

Thank you!