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A to Z of Excel Functions: the LOG Function

18 October 2021

Welcome back to our regular A to Z of Excel Functions blog.  Today we look at the LOG function.


The LOG function

Logarithm is a term coined by Scottish mathematician John Napier (1550-1617), from the Greek word logos meaning "proportion, ratio or word" and arithmos meaning "number", which therefore roughly translates to "ratio-number".

For a given base, a logarithm states the power that the base must be raised to for a given number, e.g.


The LOG function returns the logarithm of a number to the base you specify.  Its syntax is given by

LOG(number, [base])

The LOG function has the following arguments:

  • number: this is required and represents the positive real number for which you wish to determine the logarithm
  • base: this argument is optional and denotes the base of the logarithm.  If it is omitted, the base is assumed to be 10.

Please see my example below:


We’ll continue our A to Z of Excel Functions soon.  Keep checking back – there’s a new blog post every business day.


A full page of the function articles can be found here.