Electronics · Free Calculator
dBm to Watts Calculator
Convert RF and signal power between dBm and watts, and see the voltage it produces across a 50 Ω load.
dBm to mWWatts to dBmVoltage at 50 ΩRF power
dBm
Ω
Power100 mW
In dBW−10.00 dBW
RMS voltage2.236 V
Peak voltage3.162 V
Peak to peak6.325 V
In dBµV126.99 dBµV
How this result was calculated
- P = 10^((dBm − 30) ÷ 10) = 100 mW
- Vrms = √(P × R) = 2.236 V
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dBm Formulas
P (W) = 10^((dBm − 30) ÷ 10)
dBm = 10 × log10(P ÷ 1 mW)
Vrms = √(P × R)
dBm = 10 × log10(P ÷ 1 mW)
Vrms = √(P × R)
Worked example
20 dBm = 100 mW, which is 2.24 V rms across 50 Ω. 0 dBm is 1 mW or 0.224 V rms.
Key insight: every 3 dB doubles the power and every 10 dB multiplies it by ten, so 30 dBm is 1 W and 40 dBm is 10 W.
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Frequently Asked Questions
What is 0 dBm in watts?
1 mW (0.001 W).
How many dBm is 1 watt?
30 dBm.
Why is the load impedance needed?
Only to convert power into voltage; dBm itself is a power unit. RF systems usually use 50 Ω, video 75 Ω and audio 600 Ω.
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