Logarithm Calculator

Compute the logarithm of a number to any base.

Last updated: 25 Aug 2026

Quick answer

A logarithm answers "what power gives this number?" — logₐ(x). For example, log₁₀(1000) = 3 and log₂(8) = 3. Enter the number and base above.

Number

Base

Compute a logarithm to any base: logₐ(x) = ln(x) ÷ ln(a). Use base 10 for common log, or ~2.71828 for natural log.

How to calculate a logarithm

What is a logarithm?

The power a base must be raised to in order to get a number — log₁₀(1000) = 3 because 10³ = 1000.

What is natural log (ln)?

A logarithm with base e (≈2.71828); enter 2.71828 as the base to approximate it.

What is log base 2 used for?

Common in computing and information theory (bits).