In many RF calculations, the ports are often measured using an ammeter or voltmeter. To avoid the complexity of the calculations, it is convenient if all the parameters are converted into power units (dBm). dBm is a measure of power ratio in decibel (dB) referenced to one milliwatt (mW).
The following calculator can be used to convert current(A) into dBm.
The conversion of amperes to dBm is expressed as:
P (dBm) = 20 × log10(I)+10 × log10(Z) + 30
P is power in dBm
I is current in Amp
Z is the impedance of the system (usually RF systems have 50-ohms impedance).