dBm - dBw Watts Conversion Table

- chart or table to provide a conversion between power measured in dBm or dBW and power measured in watts. dBm and dBW are widely used in conjunction with RF test equipment including spectrum analyzers and signal generators.

The decibel is widely used in radio and electronics design calculations in particular it is used in many RF or radio frequency associated specifications and details.

When measuring radio frequency, or RF power, it is often easier to have a measurement made in a way that it is easy to compare the two levels.

As a result many power levels are specified in dBm or dBW, and much RF test equipment including power meters, spectrum analysers, signal generators and the like have calibrations in dBm or dBW. Often RF components such as mixers, oscillators and the like, as well as the interfaces between modules in RF equipment have their levels specified in dBm or dBW. Radio transmitters may also have their output levels expressed in this way.


What are dBm and dBW?

In itself a decibel is not an absolute level. It is purely a comparison between two levels, and on its own it cannot be used to measure an absolute level. As a result of this the quantities of dBm and dBW are used:

  • dBm - This is a power expressed in decibels relative to one milliwatt.
  • dBW - This is a power expressed in decibels relative to one watt.

From this it can be seen that a level of 10 dBm is ten dB above one milliwatt, i.e. 10 mW. Similarly a power level of 20 dBW is 100 times that of one watt, i.e. 100 watts.

A more extensive conversion table of dBm, dBW and power is given below:


dBm dBW Watts Terminology
+100 +70 10 000 000         10 Megawatts
+90 +60 1 000 000         1 Megawatt
+80 +50 100 000         100 kilowatts
+70 +40 10 000         10 kilowatts
+60 +30 1 000         1 kilowatt
+50 +20 100         100 watts
+40 +10 10         10 watts
+30 0 1         1 watt
+20 -10 0.1         100 milliwatts
+10 -20 0.01         10 milliwatts
0 -30 0.001         1 milliwatt
-10 -40 0.0001         100 microwatts
-20 -50 0.00001         10 microwatts
-30 -60 0.000001         1 microwatt
-40 -70 0.0000001         100 nanowatts
-50 -80 0.00000001         10 nanowatts
-60 -90 0.000000001         1 nanowatt

The use of the values dBm and dBW is widespread. They are found as direct calibration scales on many items of RF test equipment often being used in preference to the more elementary basic units of watts or milliwatts. Items of RF test equipment including power meters, signal generators and RF spectrum analyzers in particular use these units. Accordingly to be able to understand the RF test equipment specifications it is necessary to have an understanding of dBm and dBW. Also many RF components are also specified in terms of dBm or dBW.


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