Excel - finding the power of 2 from a result?

[AndrewT]

Hi,
I want to use Excel spreadsheet to calculate attenuation of a simple RC single pole filter.

I need a formula to give the power that 2 must be raised to when I already know the resultant of the power.
i.e.
2^X=32, then X=5
or
2^Y=47.1, then Y=?

I know that the answer that I need is Y=5.56 using a calculator but how can I get Excel to give me that answer?

[jimbo1968]

Y= log(47.1)/log(2)

[AndrewT]

Hi Jimbo,
thanks.

It works!