How this calculator works
Power SNR compares integrated signal and noise powers over the same bandwidth. Equal-impedance RMS voltage ratios are squared to obtain a power ratio. In a statistical convention, mean divided by standard deviation is an amplitude-like ratio, and its square is the power-like ratio. The simple-ratio mode makes no power or amplitude assumption.
Formula
SNR_dB = 10 log10(Ps/Pn) = 20 log10(Vs/Vn) at equal impedance. Statistical ratio = mean/SD = 1/CV; its square is power-like.
Worked example
1 W of signal and 0.01 W of noise give ratio 100 and 20 dB. RMS voltages 1 V and 0.1 V at equal impedance give the same 20 dB.
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Frequently asked questions
Why 10 log for power and 20 log for voltage?
At equal impedance, power scales as voltage squared, bringing a factor of two outside the logarithm.
Can SNR be negative in decibels?
Yes. Negative dB means the signal power is below the noise power.
Can noise be zero?
No finite decibel value exists for positive signal divided by zero noise; this tool requires positive inputs.