About the logarithm calculator
A logarithm answers the question: what power do I raise the base to in order to get this number? Logs appear in compound growth, sound levels, pH, and computer science.
How to use this calculator
- Enter a positive number.
- Choose a base, or enter a custom base.
- Read the result and the check.
Worked examples
- ln(125) ÷ ln(5) = 4.8283 ÷ 1.6094
- = 3; check: 5³ = 125
3.
Measurement guidance
Common bases
Base 10 is used for orders of magnitude, base e for continuous growth, and base 2 for bits and doubling.
Frequently asked questions
Why can’t I take the log of zero or a negative number?
No real power of a positive base gives zero or a negative number.
What is ln?
The natural logarithm, base e ≈ 2.71828.