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Log Calculator

Find a logarithm in a positive base other than one.

Calculator inputs

Worked example: Log Calculator

Log ten. This fixed reference example shows one complete scenario; the interactive results above use your current inputs.

View the example inputs
Value
100
Base
10
Calculated results for the fixed example
Calculated quantityExample result
Logarithm2

Understanding an equation’s operations and domain

Write the intended operation explicitly

Parentheses establish how a compound expression is grouped. Exponentiation, a unary minus and multiplication need not have the same precedence. The expression tool documents its supported operators and functions, and scientific calculations require the correct angle convention.

The real-number domain matters. A zero denominator, a logarithm of a nonpositive number or an even root of a negative radicand can make an otherwise familiar formula undefined in real arithmetic. Some tools explicitly return complex roots; others reject non-real results.

Check a result against the original question

A correct numeric operation can still answer the wrong question if the inputs represent different quantities. Confirm whether you are finding a percent of a base, a ratio, a distance, a root or a solution of an equation.

The worked example below makes the variables and expected output concrete. Floating-point arithmetic can round non-integer quantities; tools that use exact fractions or large integers identify that separate method.

Formula and calculation method

log_base(value)=ln(value)/ln(base); value must be positive.

Reference Sources

Frequently asked questions

How does this calculator work?

log_base(value)=ln(value)/ln(base); value must be positive.

What assumptions should I check?

Check the units and definitions shown beside each input. Results use the values you enter.

Can I save or print this calculation?

Use Copy link with inputs to reproduce the scenario, Download results for a text record, or Print. Where a schedule is shown, its CSV download includes every row.