Enter a number and a base to calculate the logarithm. Everything runs in your browser — nothing you enter here is uploaded, stored, or logged.
Calculated locally in your browser — nothing is sent to our server.
Result
How This Calculation Works
The logarithm of x to base b answers the question “what power must b be raised to, to get x?” This calculator uses the change-of-base formula (log(x) ÷ log(b), using the natural logarithm internally) so any positive base works, not just the common base-10 or base-e logarithms. Both the number and the base must be positive, and the base cannot be exactly 1 — logarithms are undefined outside those conditions.
FAQ
What is log base 10 of 100?
log₁₀(100) = 2, because 10² = 100.
Can I calculate a natural logarithm (ln)?
Yes — enter e (approximately 2.71828) as the base, or any other base you need.