Logarithm Calculator
Calculate the logarithm of a number to any base, plus the natural log (ln), log base 10 and log base 2.
Result
Logarithm
Undefined
Logarithms are only defined for numbers greater than zero.
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Enter a number and a base to compute its logarithm — the power the base must be raised to in order to get your number. Common logs (base 10, base 2 and natural log) are shown too.
Frequently asked questions
What is a logarithm?
A logarithm is the inverse of raising to a power. log_b(x) asks 'what exponent turns b into x?'. For example, log₂(8) = 3 because 2³ = 8.
What's the natural logarithm?
The natural log (ln) uses the mathematical constant e (about 2.718) as its base. It appears throughout science and finance because of how growth and decay behave.