On a calculator it is the "log" button. It is how many times we need to use 10 in a multiplication, to get our desired number. Example: log(1000) = log 10 (1000) = 3 . Natural Logarithms: Base "e" Another base that is often used is e (Euler's Number) which is about 2.71828.

For example, in order to calculate log 2 (8) in calculator, we need to change the base to 10: log 2 (8) = log 10 (8) / log 10 (2) See: log base change rule. Logarithm of negative number. The base b real logarithm of x when x<=0 is undefined when x is negative or equal to zero: