dBm stands for decibels (dB) relative to one milliwatt. It is an absolute unit of power.
How you subtract two dBm values together to find the total power?
This tool performs the subtraction of two dBm power values. Simply enter Power1 and Power2 with the appropriate units. It computes the difference
Power1 – Power2
in dBm or dBW.
Explanation
Note that since dBm is a logarithmic value you cannot subtract two dBm values directly. Instead you have to:
- Convert dBm to Watt
- Subtract Watt values
- Convert the result back to dBm
Example calculation
The difference between power levels 30 dBm and 3 dBm is 29.99 dBm (not 27 dBm).