Physics

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Noise Figure Calculator.

Calculate noise factor and noise figure from input and output signal-to-noise ratios.

On-device calculationNo signup
01

Set your values

Results update as you type.

Noise figure: 10 dB

Noise figure

0.000000dB
Noise factor: 10

Noise factor

0.000000

Results update automatically as you type.

Use Cases

Evaluate amplifier performance

Determine how much an amplifier degrades the signal-to-noise ratio. A lower noise figure means better performance for sensitive applications.

Example: Input SNR = 100, Output SNR = 50 gives noise factor 2, noise figure 3.01 dB.

Compare receiver components

Use the noise figure to compare the noise performance of different components like mixers, filters, or cables in a signal chain.

Example: Component A: NF 2 dB, Component B: NF 4 dB – A is better.

Frequently Asked Questions

What is the difference between noise factor and noise figure?
Noise factor is a linear ratio of input SNR to output SNR, while noise figure is the same ratio expressed in decibels (dB). The calculator provides both: noise factor as a linear value and noise figure in dB.
How do I use this calculator?
Enter the input SNR and output SNR in linear units (not dB). The calculator will compute the noise factor as input SNR divided by output SNR, and then convert it to noise figure in dB using the formula NF = 10 * log10(noise factor).
What does a noise figure of 0 dB mean?
A noise figure of 0 dB indicates that the output SNR equals the input SNR, meaning the device adds no noise. In practice, this is ideal and not achievable; real devices have positive noise figures.

Tips & Common Mistakes

Tips

  • Ensure both SNR values are in linear units (not dB). If you have dB values, convert them to linear using SNR_linear = 10^(SNR_dB/10).
  • For best accuracy, use precise SNR measurements from a spectrum analyzer or similar instrument.
  • Remember that a higher noise figure indicates more noise added by the device, so aim for lower values in critical paths.
  • This calculator is for reference; always verify with real-world measurements in your design.

Common Mistakes to Avoid

  • Entering SNR values in dB instead of linear. This will produce incorrect noise factor and noise figure.
  • Confusing noise factor with noise figure: noise factor is linear, noise figure is in dB. The calculator gives both, so check the units.
  • Assuming a noise figure of 0 dB is achievable; it is an ideal limit, not a practical target.

Last updated: August 13, 2026