About this Logarithm Calculator
Logarithm Calculator evaluates logs with custom bases, making it useful for algebra, scientific notation and exponential relationships.
Formula or method
log_b(x) = ln(x) ÷ ln(b).
Example
log₁₀(1000) = 3 because 10³ = 1000.
Common uses
- Evaluate common or custom-base logarithms.
- Check exponential-equation work.
- Compare growth scales.
How to use this tool
- Enter the values or text requested by the calculator.
- Choose units or options when the tool provides them.
- Select the calculation button and review the result.
- Use the formula, example and notes on this page to check whether the result fits your situation.
Important note
The value must be greater than zero and the base must be positive and not equal to 1.
Frequently asked questions
Can I use base e?
Yes. Enter approximately 2.718281828459045 as the base, or use a value suitable for your precision needs.
Why is base 1 invalid?
No power of 1 can produce different positive values, so a logarithm base of 1 is not defined.