pH can be used to calculate a concentration by using the equation pH= -log [H+]. For example, for calculating the hydrogen ion concentration of a solution with a pH of 5.5, one should rewrite the formula to solve for concentration.  [H+] concentration can be solved by rewriting the formula as  [H+]= 10^-pH. Thus,  [H+]= 10^-5.5, and equals 0.0000031622.