Information and Tips
EIRP / ERP Calculator
The EIRP / ERP Calculator helps calculate the effective radiated power of a radio system after including transmitter power, antenna gain and cable losses. It also shows the difference between EIRP and ERP, which are often confused in wireless installations.
EIRP is referenced to an isotropic antenna, while ERP is referenced to a half-wave dipole. The difference between them is 2.15 dB.
Calculate EIRP and ERP
Regulatory limits depend on country, band, channel width and application. This calculator is an engineering aid, not a legal approval tool.
Formula
EIRP [dBm] = TX power [dBm] + antenna gain [dBi] - cable loss [dB]
ERP [dBm] = EIRP [dBm] - 2.15 dB
If antenna gain is entered in dBd, the calculator converts it to dBi by adding 2.15 dB. This is important because many antenna datasheets use dBi, while some radio regulations or older documents may refer to ERP.
EIRP vs ERP
| Parameter | Reference antenna | Meaning |
|---|---|---|
| EIRP | Isotropic antenna | Equivalent isotropically radiated power |
| ERP | Half-wave dipole | Effective radiated power |
| Difference | 2.15 dB | EIRP = ERP + 2.15 dB |