free path loss calculator for wireless propogation

http://www.daycounter.com/Calculators/Friis-Calculator.phtml

This calculator computes the power that a receiving antenna receives for a given transmitting antenna for a given power for a distance greater than one wavelength for line of sight transmission. The greater the frequency the greater the path loss.

one more is http://www.terabeam.com/support/calculations/free-space-loss.php