Noise power is based on the thermal noise power at the input of the system, along with system gain and noise figure:
, where
Multiply by 1000 to obtain milliwatts and then convert to dBm units:
or, factoring out the 1000:
Now that we have the thermal noise at the input, add the system gain and the additional noise added by the system (the NF) to get the noise power at the output:
Related Pages on RF Cafe

Noise Figure <> Noise Temperature
Calculator
 Noise Power and Voltage

Cascaded Noise Figure

Noise Figure Meters & Noise Generators

Noise Sources
"Noise and Interference"  WebEE Tutorial