This calculator converts volt-per-meter (V/m) to dBm.
V/m is a measure of field intensity at any distance from the transmitter. The signal at the input of the receiver however is typically specified in terms of Volt or dBm.
There are two calculators to convert from V/m to dBm.
The first one requires the Antenna gain and Frequency of operation. It uses this to compute the Antenna Factor, RMS voltage and then power in dBm.
AF = 20*Log10(9.73/(λ√G))
V = E/10(AF/20)
Convert Antenna Factor to Power
This next calculator is used if you know the antenna factor. Many antenna vendors will provide this in a data sheet. The unit of AF is dB/m.
Typically and practically, the Antenna factor varies with frequency. Use the value of AF at a specific frequency to give you the power in dBm at that frequency as well.