ERP (Watts) Formula and Calculator

Use this calculator to find the Effective (or Equivalent) Radiated Power (ERP) in Watt, dBm and dBW.


  • Transmit Power (dBm)
  • Antenna gain (dBi)
  • Cable Loss (dB)


ERP = PTx – LC + GAnt – 2.15

where the units of ERP are dBm

ERP in Watt is

ERPW = (10ERP/10 )/1000


Effective Radiated Power is the total power radiated by a half-wave dipole antenna to give the same radiation intensity as the actual source antenna at a distant receiver located in the direction of the antenna’s strongest beam.

Antenna gain in dBi is a measure of its gain compared to an isotropic antenna. Isotropic antennas are hypothetical and radiate signal equally in all directions. An antenna with a higher dBi value has more gain than an antenna with a lower dBi value.

Cable Loss LC reduces the output signal level. It is expressed in deciBel or dB.

The transmitted power from an amplifier for instance is entered in dBm.

Related Calculators

  • EIRP or Effective Isotropic Radiated Power
  • Dipole Antenna
  • EIRP to ERP
  • ERP to EIRP