A little thought will show that the inverse pH function must look like this:

[H⁺] = 10^-pH

With this formula firmly in head, pH values can be readily estimated by looking at the exponent on the concentration. And you will be correct---as long as the acid is STRONG.

There is a companion function to pH which is sometimes very convenient--especially when dealing with bases for which a direct pH calculation cannot be done. It is called pOH:

pOH = -log[OH^-]

It is also very helpful to remember:

pH + pOH = 14