dBm to Watts Converter
Convert dBm to mW and W, or mW to dBm.
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dBm
dBm
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Milliwatts
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Watts
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dBm to Watts Converter by TheCalcTools
How the dBm to Watts Converter works
Enter a power level and choose dBm or mW.
dBm is decibels relative to 1 milliwatt: 0 dBm is 1 mW.
Every 10 dB is a factor of 10 in power, and every 3 dB is about a factor of 2.
The formula
P(mW) = 10^(dBm ÷ 10)dBm = 10 × log₁₀(P in mW)
Worked example
Using the default values shown in the calculator:
| Value | 20 |
|---|---|
| Input unit | dBm |
- 20 dBm = 10^(20 ÷ 10) mW = 100.00 mW.
- In watts that is 0.1000 W.
Result:
| dBm | 20.00 |
|---|---|
| Milliwatts | 100.0000 |
| Watts | 0.1000 |
Frequently asked questions
Why is dBm used for radio?
Signal power spans many orders of magnitude. A logarithmic scale makes it easy to add gains and subtract losses.
Can dBm be negative?
Yes. Negative dBm means less than 1 mW. A Wi-Fi signal at −60 dBm is a millionth of a milliwatt.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.