Noise Figure Calculator

Compute NF (dB), Noise Factor (F), and Noise Temperature. Supports SNR-based solving and cascaded NF (Friis).

How to Use

  1. Select a mode: From SNR, From Noise Factor, or Cascade (Friis).
  2. Enter the required values (SNR, NF, F, gains).
  3. Results update instantly; open Show Work for formulas and steps.
  4. Use Share Link to generate a restoreable URL (only on click).
NF
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F
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Te
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Ref
290 K
Pick a mode and enter values to compute noise figure and related metrics.
Inputs & Settings
Deterministic browser math. No uploads. No auto-URL updates while typing.
SNR at the input of the device/system.
SNR at the output. Noise factor uses SNR degradation.
Uses F = SNR_in / SNR_out (linear). Then NF(dB) = 10·log10(F).
Show Work (step-by-step)
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Work is shown using consistent linear math internally (with dB conversions shown explicitly).

Reference

  • Noise Factor (linear): F = SNR_in / SNR_out
  • Noise Figure (dB): NF = 10·log10(F)
  • Convert NF → F: F = 10^(NF/10)
  • Equivalent Noise Temperature: T_e = (F − 1)·T0 (T0 typically 290 K)
  • Friis (cascade): F_total = F1 + (F2−1)/G1 + (F3−1)/(G1·G2) + …
Tip: Gains in Friis must be linear (power gain). The tool converts from dB if needed.

FAQ

Is noise figure the same as SNR loss?

In linear terms, yes: F = SNR_in / SNR_out. In dB, NF equals the SNR degradation in dB.

Why does the first stage matter most in a cascade?

Friis divides later-stage noise contributions by earlier gains. A low-NF, high-gain first stage reduces total NF significantly.

What is “T0 = 290 K”?

It’s the standard reference temperature used to relate noise factor to equivalent noise temperature.

Tool Info

Last updated:

Updates may include more cascade controls, validation edge cases, and export improvements.