How this calculator works
Gain is positive when output exceeds input and negative when the signal is reduced. Use 10 times the base-ten logarithm for power. Voltage uses 20 because electrical power at fixed resistance is proportional to squared voltage. Inverse modes solve one signal magnitude; input and output must be measured on the same basis.
Formula
Gpower = 10 log10(Pout/Pin); Gvoltage = 20 log10(Vout/Vin). Output/input ratio = 10^(G/10) for power or 10^(G/20) for voltage.
Worked example
Increasing 1 W to 100 W gives 20 dB of power gain. A 20 dB voltage gain increases 2 V to 20 V at equal impedances.
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Frequently asked questions
Can gain be negative?
Yes. A negative gain describes a reduction.
Can I compare different resistances?
For power gain, use measured power or include the impedance ratio separately. The simple voltage expression assumes equal impedances.
Does 0 dB mean zero output?
No. It means equal input and output magnitudes.