Logarithm Calculator


Calculate logarithm of a number to any base:

* Use e for scientific notation. E.g: 5e3, 4e-8, 1.45e12


b y = x

Then the base b logarithm of a number x:

logb x = y

Logarithm change of base calculator

Anti-logarithm calculator


In order to calculate log-1(y) on the calculator, enter the base b (10 is the default value, enter e for e constant), enter the logarithm value y and press the = or calculate button:


y = logb x

The anti logarithm (or inverse logarithm) is calculated by raising the base b to the logarithm y:

x = logb-1(y) = b y

Logarithm rules

Logarithm product rule

logb(x × y) = logb(x) + logb(y)

Logarithm quotient rule

logb(x / y) = logb(x) - logb(y)

Logarithm power rule

logb(x y) = y × logb(x)

Logarithm base switch rule

logb(c) = 1 / logc(b)

Logarithm change of base rule

logb(x) = logc(x) / logc(b)