I have a forumla question. I have this formula x=1/2t^2. Is this the formula to find the acceleration that is caused by gravity?

Well in Kinematics..theres 1 equations that is x= v0t + .5 (a)t^2

and that your equation can be simplified to that if the initial velocity is 0...we would get x= .5(a)t^2..this is to find the distance (displacement).