# How do you calculate log_2 128?

Jun 11, 2016

${\log}_{2} 128 = 7$

#### Explanation:

There are 2 formats which are interchangeable:

Log form and index form.

${a}^{b} = c \text{ } \Rightarrow {\log}_{a} c = b$

In log form, ask the question..."to what power must 2 be raised to get 128?"

Knowing the powers of 2 is a huge advantage.
$128 = {2}^{7}$

${\log}_{2} 128 = 7$