How to Convert dBm to dB and Understand the Difference Between dB and dBm?

How do you convert the value in dBm to dB ??

If you have an expressed power level in dB, basically dB and dBm are the same. dBm is simply the power level related to 1mW. In dB mark you can have a different reference level or the same and then it will be the same as dBm
the general formula you have is this:

P [dB] = 10log (P [W] / Po [W]) where: Po - reference power

i.e. appropriately for dBm you have

P [dBm] = 10log (P [W] / 1mW)

If the voltage level (current etc) was in decibels, then instead of 10log in the formula there is 20log.
I hope you understood some of this and that I was right ) - I knew it a year ago )

A useful table is here http://republika.pl/elektronikjk/p.html.

There is a simple way to convert the measured value in dB and dBm.

When converting power 10log (P)
If you already have a value in dB, then adding 30 to it you get the value in dBm
e.g. 10dB -> 40dBm
Converting from dBm to dB is by subtracting 30

When converting from the second formula, e.g. 20log (U1 / U2)
If you have a value in dB then you have to add 60 and you already have dBm.
If you have dBm, minus 60, you get dB.

Thanks for the advice. The case is a bit more complicated (at least I think so): It reads the value from the analyzer, e.g .:
- 80 dBm. I have to convert it to dB to plot it on the graph. According to another instrument that measures in dB, it should be around 40 dB. This includes the input impedance of the instrument, etc.
If you are interested, please visit the WORKSHOP section, topic WIDMA ANALYZER.