dBm Calculator


dBm is the power ratio of measured power referenced to 1 milliwatt (mW) in decibels (dB).

    \[P_{o,mW} = \frac{V_{p}^2}{2R_L}/1mW\]

(1)   \begin{eqnarray*} P_{o,dBm} &=& 10 ~ \log (P_{o,mW}) \\ &=& 20 ~ \log (V_p) - 10 ~ \log (2 R_L) + 30 \end{eqnarray*}

A change in power ratio by a factor of 10 is a 10 dB change.
A change in power ratio by a factor of 2 is approximately a 3 dB change.

Voltage across 50\Omega load, at 10dBm –> 1V
For every 10x in voltage, power increases by 20dB.

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