Enter any integer or numerical value into the calculator and select a base value to determine the negative log of that number.

Negative Log Formula

The following formula is used to calculate a negative log.

x = Log_b(1/a) 
  • Where X is the negative log
  • b is the base value
  • a is the number the negative log is taken of

Negative Log Definition

What is a negative log? A negative log is defined as the number of times required that 1 must be divided by the base in order to achieve the log number. So, -Log2(.5) = 1. Since 1/2 = -.5.


How to calculate a negative log? Calculating the negative log is as simple as performing the normal log function on 1/x instead of x. The base stays the same. For example, the negative log of -log(10) = log(1/10) = 1.

Negative Log FAQ

Is a negative log the same as antilog? In most cases, the terms negative log and antilog are used interchangeably.

Can you calculate a negative log? Calculating a negative log is as simple as using the formula x = Logb(1/a) , where x = -logb(a).