To find the logarithm of a number other than a power of 10 you need to use your scientific calculator or pull out a logarithm table if they still exist. The power to which the base e e 2718281828 must be raised to obtain a number is called the natural logarithm ln of the number. When you and I calculate two plus two we imagine a number line start at two and hop over a couple of spots to get to four or at least we did until we memorized the answer.
Learn how to evaluate basic logarithms.
Choose a number very close to the original number that you can construct using factors whose logarithms you have learnt. 10 X 100 is the exponential form of the expression and log100 X is the logarithmic form. On a calculator it is the ln button. For example to evaluate the logarithm base 2 of 8 enter ln.