Resistor Noise Calculator
Calculate thermal noise voltage (RMS)
Room temperature ≈ 298 K (25°C)
Audio bandwidth example: 20 kHz
How to Use This Calculator
1
Enter Resistance
Provide the resistor value in ohms (Ω).
2
Enter Temperature
Use Kelvin. Room temperature ≈ 298 K.
3
Enter Bandwidth
Measurement bandwidth in Hz. Wider bandwidth yields higher noise.
Formula
vn,rms = √(4 k T R B)
Where:
- k = Boltzmann constant (1.380649 × 10⁻²³ J/K)
- T = Temperature (K)
- R = Resistance (Ω)
- B = Measurement bandwidth (Hz)
Example: R = 1 kΩ, T = 298 K, B = 20 kHz → vn ≈ 0.57 µV RMS.
About Resistor Noise
Thermal (Johnson) noise is an unavoidable voltage noise generated by resistors due to the random motion of charge carriers.
Notes
- Noise is broadband; limit bandwidth to reduce noise.
- Lower resistance reduces noise for a given bandwidth.
- Cooling reduces kT and therefore noise.
Frequently Asked Questions
Does resistor type matter?
Thermal noise depends only on R, T, and bandwidth. Composition affects excess 1/f noise, which is not modeled here.
What about current noise?
This calculator reports voltage noise. Equivalent current noise is vn/R for a Thevenin source.