Resistor Thermal Noise Calculator
Calculate resistor open-circuit RMS noise, spectral density, short-circuit noise current and matched-load noise power.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Apply the classical thermal-noise white spectral density and integrate over entered equivalent noise bandwidth.
Vrms=√(4kTRB); voltage density=√(4kTR); available matched power=kTB
Worked example
At 300 K a 1 kΩ resistor has open-circuit density about 4.07035 nV/√Hz. Integrating a 20 kHz equivalent noise bandwidth gives about 0.5756 μV RMS.
Assumptions and input details
Absolute temperature must exceed zero and is limited to 10000 K. Boltzmann k=1.380649×10⁻²³ J/K is exact in SI. The bandwidth is ENBW, not an automatically inferred −3 dB bandwidth. This classical low-frequency model excludes quantum corrections, excess/1/f noise and frequency-dependent impedance. Matched-load available power is different from open-circuit mean-square voltage.
References: Analog Devices: resistor thermal-noise expression
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
SI prefixes are explicit: for example, milli means one thousandth, micro one millionth and kilo one thousand. Changing a unit changes the interpretation of the entered number.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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