How to use this calculator
Choose power, root, logarithm, or solve b^x=a. Enter a and b.
Formula and method
log_b(a)=ln(a)/ln(b). For b^x=a, x=log_b(a). Odd roots of negative numbers are negative real numbers.
Worked example
4th root of 16 = 2; log base 2 of 16 = 4.
Assumptions and supported scope
Real domain only. Root index is an integer 1–100; even roots of negatives are rejected. Log inputs and bases must be positive, base ≠1. Floating-point results are approximate.
Method references
Method and worked example checked against the calculator implementation. About our methods · Report a correction