text: All you have to remember is that log (base a) of b = c means exactly the same thing as a^c = b. Thus, if you take a standard log of that equation, you get log(a^c) = log b, so c log a = log b, so c = log b / log a.\n\nThus, that gives you the precise way of working out such a log - take one of the normal logs of the number, then divide by the same log of the base.