What is SNR?
SNR stands for signal-to-noise ratio. This ratio is a measure of the strength of the desired signal relative to the current level of background noise. Our signal-to-noise ratio calculator is a tool that helps you find the ratio of the desired signal to the background noise. Below are some signal-to-noise ratio examples we use in the real world:
- Finding isotope levels in ice cores;
- Measuring the efficiency of a cell's biochemical signaling;
- Determining a car amplifier's sound clarity; and
- Computing a communication channel's bandwidth and capacity 📡.
Signal-to-noise ratio calculator
Our signal-to-noise ratio calculator is a convenient tool that calculates the ratio between the desired signal level and the acceptable background noise. Imagine you are having a conversation with a friend at a quiet café — your voice is the signal, easily heard. Now picture the same conversation at a loud concert: the music is the noise, and your friend keeps getting cut off. SNR captures exactly that comparison as a single number.
In the tool, you select the type of SNR; whichever type you choose, you need to input:
- The magnitude of the signal; and
- The magnitude of the noise.
Each type has various units associated with it. Some may appear unitless, but remember they can be of any appropriate unit as long as both signal and noise are in the same units — the units cancel out in the ratio.
What is a good signal-to-noise ratio?
The signal-to-noise ratio is usually expressed as a single numerical value in decibels (dB). The ratio can be zero, positive, or negative:
- SNR > 0 dB — the signal strength is higher than the noise level (good 👍).
- SNR = 0 dB — the signal has the same strength as the noise.
- SNR < 0 dB — the signal is weaker than the noise (poor 👎).
The greater the SNR value, the stronger the signal is in comparison to the noise, which means transmission will be more efficient and accurate. A low SNR means the noise disrupts data transfer of text, images, audio, video streams, or telemetry.
How to calculate signal-to-noise ratio? SNR formula
This calculator includes five different SNR formulae, so you can calculate various types of SNR based on your input signal and the units you measure the data in:
| Type | Formula |
|---|---|
| Signals ratio (absolute units) | SNR = signal / noise |
| SNR from decibels | SNR (dB) = signal (dB) − noise (dB) |
| Power SNR | pSNR = 10 × log₁₀(signal / noise) |
| Voltage SNR | vSNR = 20 × log₁₀(signal / noise) |
| From coefficient of variation | SNR = μ / σ and SNR = μ² / σ² |
Where:
- SNR (dB) — the signal-to-noise ratio in decibels;
- pSNR — the power signal-to-noise ratio;
- vSNR — the voltage signal-to-noise ratio;
- μ (mu) — the signal mean; and
- σ (sigma) — the standard deviation of the noise.
💡 Remember, the logarithmic base is always 10 in the equations above.
Signal-to-noise ratio example
For instance, if your signal is 6 volts and the noise is 4 volts, select Voltage SNR. The result is:
vSNR = 20 × log₁₀(6 / 4) = 20 × log₁₀(1.5) ≈ 3.522 dB
Signal-to-noise ratio requirements
SNR calculation is an essential concept in science and engineering — it can measure any form of signal or transmission. The right requirement depends on the application:
- Wi-Fi / wireless networks: 20 dB is acceptable, 25–40 dB is good, and above 40 dB is excellent.
- Audio equipment: a higher SNR means cleaner sound with less background hiss.
- Scientific measurement: a higher SNR makes a faint signal easier to distinguish from random noise.
Measurement systems: metric & imperial
Because SNR is a dimensionless ratio, the same value is obtained whether you work in the metric (SI) or the American/imperial system — as long as both the signal and the noise are expressed in the same unit. For example, volts and volts, watts and watts, pascals and pascals, or psi and psi will all yield an identical ratio.
FAQs
What does a negative SNR mean?
A negative signal-to-noise ratio means the noise is stronger than the signal. In practice, the desired information is buried under the background noise, so the transmission is unreliable.
Why is the power SNR multiplied by 10 and the voltage SNR by 20?
Power is proportional to the square of voltage (P ∝ V²). Converting a power ratio to decibels uses 10 × log₁₀, while converting a voltage (amplitude) ratio uses 20 × log₁₀, because log₁₀(V²) = 2 × log₁₀(V).
What is the coefficient of variation method?
When you have repeated measurements, the SNR can be estimated as the signal mean (μ) divided by the standard deviation of the noise (σ): SNR = μ / σ. The squared form, μ² / σ², gives the power signal-to-noise ratio.
Do the units of signal and noise matter?
Only that they match. The ratio is unitless, so volts/volts, watts/watts, or any consistent pair gives the same result. If the signal and noise are in different units, convert one of them first.