Signal-to-Noise Ratio Calculator
Compute the signal-to-noise ratio from a signal and noise level — as a plain ratio and in decibels, for amplitude or power quantities.
How it works
SNR = signal ÷ noise · dB = 20·log₁₀(SNR) [amplitude] or 10·log₁₀(SNR) [power]
Signal-to-noise ratio measures how much a meaningful signal stands out from background noise — often the mean divided by the standard deviation of a measurement. As a plain ratio, higher is cleaner. In decibels the ratio is compressed logarithmically: amplitude quantities (voltage, sound pressure) use 20·log₁₀, while power quantities use 10·log₁₀, because power scales with the square of amplitude.
Worked example
A signal of 40 against noise of 5 gives an amplitude SNR of 40 ÷ 5 = 8. In decibels that is 20·log₁₀(8) ≈ 18.06 dB — a strong, clearly distinguishable signal.
Sources: Signal-to-noise ratio — Wikipedia
Frequently asked questions
Why are there two decibel formulas?
Decibels compare power. Amplitude quantities like voltage relate to power by a square, so their ratio is scaled by 20·log₁₀, whereas power itself uses 10·log₁₀. Using the wrong factor doubles or halves the dB figure.
What does SNR = 1 mean?
A ratio of 1 (0 dB) means the signal and noise have equal magnitude — the signal is barely detectable. Ratios below 1 mean the noise dominates.
How does SNR relate to the coefficient of variation?
When signal is the mean and noise is the standard deviation, SNR is exactly the reciprocal of the coefficient of variation. A high SNR corresponds to a low relative variability.
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