Logarithm Calculator

Calculate log of a number with a given base.

Logarithm formula
logab
Number a
Base b
Result:

What Is a Logarithm?

A logarithm answers the question: "To what power must I raise the base to get this number?"

If by = x, then logb(x) = y.

For example: 23 = 8, so log2(8) = 3.


<h3>Common Logarithm Bases</h3>
<p><span class=Base 10 (common log): Written as log(x) or log10(x). Used in science, engineering, and pH calculations.

Base e (natural log): Written as ln(x). The inverse of ex. Essential in calculus, growth/decay models, and statistics.

Base 2 (binary log): Written as log2(x). Used in computer science for algorithm complexity, data structures, and information theory.

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Common Logarithm Bases

Base 10 (common log): Written as log(x) or log10(x). Used in science, engineering, and pH calculations.

Base e (natural log): Written as ln(x). The inverse of ex. Essential in calculus, growth/decay models, and statistics.

Base 2 (binary log): Written as log2(x). Used in computer science for algorithm complexity, data structures, and information theory.

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lg b
Base b
Result:

How to Change Logarithm Base

To convert between bases, divide the log in the target base by the log of the original base in the target base:

logb(x) = ln(x) / ln(b) = log10(x) / log10(b)

The calculator handles this conversion automatically — just enter your number and desired base.

ln b
Base b
Result:
loga(b × c) = logab + logac
logabc = logab - logac
logabn = n × logab