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Logarithm calculator

Find the logarithm, base, or argument. The base can be a number or e.

Get started

  1. Use the example values or enter your own measurements.
  2. Calculate, then copy the result or download the available details.

Example

Input

Base 3, argument 81

Expected result

4

Try it

Good to know

The calculation runs in your browser. Use consistent units in fields with no explicit unit.

Calculation method

The logarithm log₍b₎(x) is the exponent y satisfying bʸ = x. The change-of-base formula divides ln(x) by ln(b).

log⁡b(x)=ln⁡xln⁡b,b>0,b≠1,x>0\log_b(x)=\frac{\ln x}{\ln b},\qquad b>0,\quad b\ne1,\quad x>0

Calculation mode

Logarithm
  • Base (number or e)
  • Argument
Base
  • Argument
  • Logarithm
Argument
  • Base (number or e)
  • Logarithm