Calculators

The Friis Transmission Equation is used to calculate the power received at an antenna from another antenna at a specified distance, and transmit frequency. It is derived by assuming that free space is lossless, and observing that under such conditions the radiated power through the surface of a sphere enclosing the transmitting antenna is independent of the sphere radius. This means that the power density decreases with the square of the sphere radius, and therefore so does the power that may be captured by a receive antenna positioned at the same distance.

The calculator below uses the Friis Transmission Equation to calculate any of the three variables (frequency, distance, and free-space path loss) from the other two. To use it, select the variable you wish to calculate and enter values for the other two.