Decibel (dB, dBm) Calculator
Convert power and voltage ratios to decibels and back, and convert between dBm and watts, with the logarithm formula shown for each answer.
Runs on your device
Result
Results appear here as you type.
What it does
Power ratios use 10·log₁₀ and voltage (or current) ratios use 20·log₁₀, because power is proportional to voltage squared. dBm is power relative to 1 mW.
How to use it
- Choose the conversion.
- Enter the value(s).
- Read the result and formula.
Example
A 100× power gain is 20 dB. Select Try an example above to see it.
When it helps
- Amplifier gain and attenuator calculations.
- RF link budgets.
- Communication systems coursework.
Questions
Is 3 dB double the power?
Yes, almost exactly: 10^(3/10) = 1.995.
What is 0 dBm?
1 milliwatt. 30 dBm is 1 W.
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