How to Use LOG and LOG10 in Excel

LOG10 turns power ratios into decibels and LOG with a base counts octaves — two log functions for real audio work.

You will learn to

• Convert a power ratio to decibels with LOG10
• Count octaves with a base-2 LOG
• Calculate the gain of a whole signal chain

How it works

LOG10(number) returns the base-10 logarithm: =LOG10(1000) is 3. It is the basis of decibels — a power gain in dB is =10*LOG10(output/input) — and of pH, the Richter scale and “orders of magnitude”.

LOG(number, [base]) lets you choose the base and defaults to 10 when you leave it out. =LOG(8,2) is 3, so =LOG(high/low,2) counts the octaves between two frequencies. For the natural log (base e), use LN.

=10*LOG10(C2/B2)