Use this tool to convert from Watt to dBm. You can select either Milliwatt, Microwatt, Nanowatt or Picowatt.
Watt to dBm Formula
PdBm = 10*log10(PmW)
where
- PmW is the power expressed in milliwatt.
- PdBm is the power expressed in dBm
What is dBm?
dBm is a unit of power expressed in deciBels referenced to one milliwatt.
It is commonly used in Radio frequency, Microwave and Optical communication systems as a measure of absolute power. It is used due to the ease of representing both very large and very small values with few digits.
For example 10,000,000,000,000 mW = 1013 mW = 130 dBm
As well, it makes RF budget calculations simpler than with linear values.
How to convert from Watt to dBm
To find the dBm equivalent of 1 W, first convert it to milliwatt. In this case, it is 1000. In general the value in Watt is multiplied by one thousand to convert to milliWatt.
The next step is to perform the calculation: 10*Log10(1000)= 10*3 = 30 dBm.
1 Watt is therefore equal to 30 dBm. This equivalence is often used by RF engineers and a baseline from which other calculations can be performed.
Let’s take a look at an example below.
What is the dBm equivalent of 2 Watt? The same calculation can be performed to give 10*Log10(2000) = 10*3.3 = 33 dBm.
Alternatively, we can see that 2 Watt is equivalent to two times 1 Watt or it represents a ratio of 2:1. This is linear ratio is equivalent to 3 dB. Therefore we can add 30 dBm + 3 dB to give 33 dBm.
With practice is becomes easier to identify these relationships for quick mental conversions but until then you can use the calculator on this page.