Logarithm Calculator
Enter a number and a base to find its logarithm. Base 10 is the default.
Logarithm
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How it works
log_b(x) = ln(x) / ln(b)Frequently Asked Questions
Which bases can I use?
Any positive base except 1. Common choices are 10 (common log) and 2 (binary log).
Why does it say undefined?
Logarithms are only defined for a positive number and a positive base that is not 1.