# 1.2.2 Noise figure and Noise factor

Noise figure (NF) and noise factor (F) are measures of degradation of the signal-to-noise ratio (<span data-highlighted="true" data-vc="highlighted-text"><span class="_kqswh2mm"><span class="_5pioz8co _189e1dm9 _1il9buyh _19lc184f _d0altlke" data-testid="definition-highlighter">SNR</span></span></span>), caused by components in a radio frequency (RF) signal chain. It is a number by which the performance of an amplifier or a radio receiver can be specified, with lower values indicating better performance.

The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise. The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise, or the ratio of input <span data-highlighted="true" data-vc="highlighted-text">SNR</span> to output <span data-highlighted="true" data-vc="highlighted-text">SNR</span>.

The noise figure is simply the noise factor expressed in decibels (dB).

[![image.png](https://wiki.cept.org/uploads/images/gallery/2026-02/scaled-1680-/8M4H3QtU6FS7ICCx-image.png)](https://wiki.cept.org/uploads/images/gallery/2026-02/8M4H3QtU6FS7ICCx-image.png)