▣ CALCULATORS Updated July 25, 2026

Logarithm Calculator

log10, ln, log2, and custom-base logarithms.

Number
Custom base
Result
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How it works

Logarithms in an arbitrary base are derived with the change-of-base rule, log_b(x) = ln(x) / ln(b), evaluated at double precision.

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Frequently asked questions

Why must the number be positive?

Logarithms of zero or negative numbers are undefined over the real numbers.

What is a natural log?

It is the logarithm in base e (about 2.71828), written ln, and it appears throughout growth and decay maths.

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