Logarithm Calculator
Find the logarithm of a number to base 10, base e or base 2.
Quick answer: enter your details below and click Calculate — your result appears instantly, right here in your browser. Nothing you enter is uploaded or stored.
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Calculators
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How to use
- Choose a base: 10, e or 2.
- Enter a positive number.
- Calculate to see its logarithm.
About this tool
Pick a base and enter a positive number. The logarithm answers the question: to what power must I raise the base to get this number? Base 10 is common in science, base e is the natural logarithm used in growth and decay, and base 2 is common in computing.
Frequently asked questions
Why can I not take the logarithm of zero or a negative number?
Because no power of a positive base ever gives zero or a negative result, so those logarithms are not defined for real numbers.
What is the natural logarithm?
It is the logarithm to base e, where e is about 2.718. It shows up in compound growth, decay and many natural processes.