dBm to Watts Converter
Convert between dBm and watts for RF power measurements used in radio, telecom, and antenna work, free and instant.
Enter Values
Minimum 0
How to use this calculator
- Enter the power in dBm, or in milliwatts.
- Read the converted value in dBm, milliwatts and watts.
How it works
The dBm to Watts Converter switches between the logarithmic dBm scale used for radio power and linear milliwatts/watts.
dBm = 10·log₁₀(power in mW), and power in mW = 10^(dBm ÷ 10). Because it's logarithmic, every +3 dB roughly doubles the power and every +10 dB is ten times the power. 0 dBm = 1 mW and 30 dBm = 1 W.
Worked example
A 30 dBm transmitter. 30 dBm = 10^(30/10) = 1000 mW = 1 watt — a common legal limit for Wi-Fi EIRP in some regions.
Frequently asked questions
What is dBm?
dBm is power expressed in decibels relative to one milliwatt. It's used in radio and networking because signal levels span a huge range, and the log scale keeps the numbers manageable.
What does +3 dB mean?
Each +3 dB is approximately double the power, and each +10 dB is ten times the power. So 23 dBm is about twice 20 dBm.
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Cite this tool
Zerdly. (2026). dBm to Watts Converter. Retrieved from https://www.zerdly.com/tools/dbm-to-watts-converter/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.