dBm is a logarithmic power unit
Zero dBm equals one milliwatt. Every increase of 10 dB multiplies power by ten, while a decrease of 10 dB divides power by ten.
Negative dBm values can be normal
Received cellular signals are tiny and often expressed as negative dBm. A less negative value represents more received power, but it does not guarantee better speed.
Power and signal quality answer different questions
dBm describes power. Interference, noise, network capacity and radio quality measurements are also needed to understand connection performance.
Frequently asked questions
How do I convert dBm to mW?
Use mW = 10^(dBm/10). For example, 0 dBm is 1 mW and 10 dBm is 10 mW.
How do I convert mW to dBm?
Use dBm = 10 × log10(mW). The milliwatt value must be greater than zero.
Is -100 dBm equal to weak transmit power?
Not necessarily. On a phone it often describes received signal power after path loss, not the transmitter output.