Signal-to-Noise Ratio Calculator
Signal-to-noise ratio in decibels, from power or voltage levels. Also gives the effective number of bits for a converter and the theoretical data rate for a channel.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
SNR(dB) = 10 × log₁₀(P_signal ÷ P_noise) ENOB = (SNR − 1.76) ÷ 6.02 C = B × log₂(1 + SNR)
The 6.02 in the ENOB expression is the decibels each extra bit buys you, and 1.76 is the quantisation noise of an ideal converter. Shannon’s capacity is the hard ceiling on error-free data rate for a given bandwidth and noise — it says nothing about how to reach it, only that nothing can exceed it.
What to watch out for
Three readings of the same number:
- As decibels — how far the signal stands above the noise floor. Speech is intelligible around 10 dB; broadcast audio wants 60 dB or better.
- As effective bits — for an ADC or DAC, the resolution you really have. A 16-bit part with 90 dB of SNR is delivering about 14.7 bits; the rest is buried in noise.
- As channel capacity — Shannon's limit on error-free throughput. It is why a noisy link cannot be fixed by cleverer coding past a point, only by more bandwidth or more power.
Frequently Asked Questions
What is a good signal-to-noise ratio?
It depends entirely on the application. Around 10 dB for intelligible speech, 20 dB for a usable Wi-Fi link, 60 dB or more for broadcast audio, and 90 dB-plus for precision measurement.
How do I calculate SNR in dB?
Take 10 × log₁₀ of the signal power divided by the noise power. If you measured voltages rather than powers, use 20 × log₁₀ instead — a signal 100 times the noise voltage is 40 dB.
What is ENOB?
Effective number of bits — the resolution a converter actually delivers once its own noise and distortion are counted. ENOB = (SNR − 1.76) ÷ 6.02, and it is always lower than the nominal bit depth.