Excel LOG Function

The LOG function returns the logarithm of a given number, using the provided base.

The LOG function takes two arguments, number and base. The value provided for number should be a positive real number. The base argument represents the base of the logarithm. Base is optional and defaults to 10 if not provided.

Examples

The logarithm of 16 with base 2 (the power to which 2 must be raised to equal 16) is 4:

=LOG(16, 2) // returns 4

The logarithm of 100 with base 10 (the power to which 10 must be raised to equal 100) is 2:

=LOG(100,10) // returns 2

Because the base argument defaults to 10, the formulas below are equivalent:

=LOG(100,10) // returns 2
=LOG(100) // returns 2

The LOG10 function also returns the base 10 logarithm of a number:

=LOG10(100) // returns 2
=LOG10(1000) // returns 3

Notes

• If number or base are not numeric, LOG returns #VALUE!
• The LOG10 function also returns the base 10 logarithm of a number.