# Signal-to-Noise Ratio Calculator

URL: https://speedycalculator.com/calculators/physics/signal-to-noise-ratio/
Last updated: 2026-10-30

> The signal-to-noise ratio calculator finds SNR as a simple ratio, converts SNR between ratio and decibels, computes power and voltage SNR in dB, and gives SNR from the coefficient of variation (mean / standard deviation).

## Inputs

- Type of SNR
- Signal (power, voltage or mean)
- Noise (power, voltage or standard deviation)
- SNR in dB

## Results

- Signal-to-noise ratio
- SNR in decibels
- Amplitude ratio

## Formula

```
SNR = S/N · SNR_dB = 10·log₁₀(P_s/P_n) = 20·log₁₀(V_s/V_n) · SNR = μ/σ
```

## Explanation

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

FieldWhat to enterType of SNRChoose one: Simple ratio, SNR from dB, Power SNR, Voltage (amplitude) SNR …Signal (power, voltage or mean)A numberNoise (power, voltage or standard deviation)A numberSNR in dBA 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 ratio55007.5750101,00012.51,250151,500202,000

## 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.

## FAQ

**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.


## Sources

- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)
- [NIST – Measurement uncertainty and SNR](https://www.nist.gov/)