Resistor Noise Calculator

Free Resistor Noise Calculator — compute the Johnson–Nyquist thermal noise voltage produced by a resistor.

850.1K uses Updated · 2026-05-11 Runs locally · zero upload
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The Resistor Noise Calculator evaluates the Johnson–Nyquist thermal noise produced by a resistor, returning both the noise voltage density and the total RMS noise over a chosen bandwidth.

How to Use Resistor Noise Calculator

  1. Enter resistance R — typically in ohms or kilohms.
  2. Enter the temperature T — in kelvin, typically 290 K (room temp) or 77 K (LN₂).
  3. Enter the bandwidth B — choose the system bandwidth in Hz, kHz or MHz.
  4. Read the noise voltage — total Vrms over the band and the equivalent noise density in nV/√Hz.

Formula & Theory — Resistor Noise Calculator

Vrms = sqrt(4 · k · T · R · B)
Vn / sqrt(Hz) = sqrt(4 · k · T · R)
k = 1.380649e-23 J/K

Use Cases for Resistor Noise Calculator

  • Low-noise amplifiers — choose feedback resistors that meet noise floor targets.
  • Sensor front-ends — estimate the noise budget for piezoresistive and bridge sensors.
  • RF & analog design — quantify thermal noise in matching networks and attenuators.
  • Teaching & lab work — visualize how resistance, temperature and bandwidth set Johnson noise.

Frequently asked questions about Resistor Noise Calculator

What is Johnson noise?

Johnson–Nyquist noise is the thermal agitation of charge carriers in a resistor, producing a broadband Gaussian voltage even without external excitation.

Does cooling a resistor reduce its noise?

Yes — thermal noise scales with √T, so cooling from 290 K to 77 K cuts the RMS noise by roughly a factor of 1.9.

Is this the dominant noise in a circuit?

It often is at moderate impedance and bandwidth, but real circuits can be dominated by 1/f noise, shot noise or external interference depending on the design.

Is my data stored?

No. All calculations run locally in your browser; nothing is sent to any server.