Use this calculator to find the max output power of a transmitter in Watt from the antenna gain (dBi) and Effective Isotropic Radiated Power (EIRP).

**Formula**

**P _{Tx}** = EIRP +

**L**

_{C}– G_{Ant}**Example Application**

The maximum EIRP for a LoRa device operating at 868 MHz is +16 dBm. The maximum antenna gain is specified to be 2.15 dBi.

Using these numbers and a cable loss of 2 dB, the maximum output power from the transmitter is restricted to** 0.038 Watt**.