The signal-to-noise ratio compares the level of a wanted signal with the background noise. It sets the quality of audio, the range of radio links, the sharpness of photographs and the detection limit of measurements.
How to use the Signal-to-Noise Ratio Calculator
- Type of SNR
- Signal (power, voltage or mean)
- Noise (power, voltage or standard deviation)
- SNR in dB
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the type. Power quantities use 10·log₁₀, amplitude quantities (voltages, sound pressures) use 20·log₁₀.
Inputs explained
| Field | What to enter |
|---|---|
| Type of SNR | Choose one: Simple ratio, SNR from dB, Power SNR, Voltage (amplitude) SNR … |
| Signal (power, voltage or mean) | A number |
| Noise (power, voltage or standard deviation) | A number |
| SNR in dB | A number |
Example values
How the main result changes when Signal changes and everything else stays at the example values above:
| Signal (power, voltage or mean) | Signal-to-noise ratio |
|---|---|
| 5 | 500 |
| 7.5 | 750 |
| 10 | 1,000 |
| 12.5 | 1,250 |
| 15 | 1,500 |
| 20 | 2,000 |
Formula
SNR = S/N · SNR_dB = 10·log₁₀(P_s/P_n) = 20·log₁₀(V_s/V_n) · SNR = μ/σ
Worked example
Inputs — Type of SNR: Power SNR; Signal (power, voltage or mean): 10; Noise (power, voltage or standard deviation): 0.01.
Results — Signal-to-noise ratio = 1,000; SNR in decibels = 30 dB; Amplitude ratio = 31.622777.
Key terms
- Decibel
- Ten times the base-10 logarithm of a power ratio.
Frequently asked questions
What is a good SNR?
Audio: above about 90 dB for hi-fi; Wi-Fi: 25 dB or more for good throughput.
Why 20·log for voltage?
Power is proportional to voltage squared.
Can SNR be negative in dB?
Yes – when the noise is stronger than the signal.
What is the Rose criterion?
In imaging, an SNR of about 5 is needed to reliably see a feature.