How much more acidic is 2 than 5?

To determine how much more acidic one number is than another on a pH scale, we use the fact that each whole number change in pH represents a tenfold change in acidity. Therefore, a pH of 2 is 10^3 (or 1,000 times) more acidic than a pH of 5, since the difference between 2 and 5 is three units.