# Difference between dBm and dB ?

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Difference between dBm and dB ?
posted Apr 6, 2014

This one is very simple, allow me to share just the link http://bit.ly/1idVd45

dBm and dB both are used to measure power level.
dBm is used to measure power with reference of 1 milliwatt. I mean to say power level is calculated using following formula:

dBm = 10 * log (P2/1milliwatt).

Whereas decibel is used for ratio of two power level using the following formula:
dB = 10 * log (P2/P1).

answer Apr 6, 2014
1. dB is used to quantify ratio between two intensity or power values while dBm is used to express an absolute value of power.
2. dB is a dimensionless unit while dBm is an absolute unit.
3. dB is relative often relative to the power of the input signal while dBm is always relative to 1 mW signal.
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