dBm to Watts Converter
Convert RF power between dBm and Watts, with milliwatt and kilowatt display, in both directions.
What dBm is
dBm expresses power in decibels relative to 1 milliwatt. Being logarithmic, dBm turns gain and loss chains (antenna gain, cable loss, amplifier gain) into simple addition and subtraction, which is why RF datasheets and specs almost always use it instead of raw Watts.
dBm to Watts formula
Watts = 10^(dBm / 10) / 1000. So 0 dBm is exactly 1 mW, 30 dBm is 1 W, 40 dBm is 10 W, 43 dBm is about 20 W, every extra 10 dBm multiplies the power by 10.
Watts to dBm formula
dBm = 10 × log10(Watts × 1000). This is the same relation solved the other way, used whenever a transmitter's power is specified in Watts and needs converting for a link budget or EIRP calculation in dBm.
Quick reference values
0 dBm = 1 mW. 10 dBm = 10 mW. 20 dBm = 100 mW. 30 dBm = 1 W. 33 dBm = 2 W. 40 dBm = 10 W. 43 dBm = ~20 W. 46 dBm = ~40 W. 50 dBm = 100 W.
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Frequently Asked Questions
What is dBm?
dBm is power expressed in decibels relative to 1 milliwatt. It is logarithmic, which makes it convenient for RF work because gains and losses along a signal chain can simply be added or subtracted instead of multiplied.
How do I convert dBm to Watts?
Watts = 10^(dBm / 10) / 1000. For example 30 dBm equals 10^3 / 1000 = 1 Watt, and 43 dBm equals about 20 Watts.
How do I convert Watts to dBm?
dBm = 10 x log10(Watts x 1000). For example 1 Watt (1000 milliwatts) gives 10 x log10(1000) = 30 dBm.
What is 0 dBm in Watts?
0 dBm equals exactly 1 milliwatt (0.001 Watt), the reference point the dBm scale is built from.
Why does RF equipment use dBm instead of Watts?
Because dBm is logarithmic, it lets engineers add and subtract gains and losses (antenna gain, cable loss, amplifier gain) along a signal path with simple arithmetic, instead of multiplying and dividing ratios in Watts.
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