Definition: dBm

(DeciBels at 1 Milliwatt) A measurement of power using one milliwatt as the reference point (0 dBm). For example, a signal at .1 milliwatt (100 microwatts) is a loss of 10 dBm. A radio station transmitting 50,000 watts of power may wind up attenuating to only a couple milliwatts by the time it is picked up by a radio receiver. See deciBel and dBA.

  dBm TO WATTS CONVERSION
                            Watts

  +40 dBm = 10 watts        10.0
  +30 dBm = 1 watt           1.0
  +20 dBm = 100 milliwatts    .1
  +10 dBm = 10 milliwatts     .01
    0 dBm = 1 milliwatt       .001
  -10 dBm = 100 microwatts    .0001
  -20 dBm = 10 microwatts     .00001
  -30 dBm = 1 microwatt       .000001
  -40 dBm = 100 nanowatts     .0000001