How it works
Calculate a logarithm in any positive base except one. Both the number and base must be positive.
log_b(a) = ln(a)/ln(b)
Worked example
Show example inputs and result
Number: 100 · Base: 10.
- Result
- 2
Questions and answers
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy