Noise Floor Calculator

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Calculate thermal noise power, system noise floor, RMS noise voltage, and receiver sensitivity estimate from bandwidth, temperature, noise figure, and required SNR.

Input Parameters

Noise Bandwidth

MHz

Use channel bandwidth or measurement bandwidth.

Temperature

290 K is standard room-temperature reference.

System Noise Figure

Receiver or measurement chain noise figure.

Required SNR

Minimum SNR required for detection or demodulation.

Input Resistance

Used only for RMS noise voltage estimate.

Results

Thermal Noise Power

System Noise Floor

RMS Noise Voltage

Estimated Sensitivity

Noise Density

Design Note

Equations Used

Thermal Noise Density: -174 dBm/Hz at 290 K

Thermal Noise: Pn = -174 + 10log10(BW) + 10log10(T/290)

System Noise Floor: Psystem = Pn + Noise Figure

RMS Noise Voltage: Vn = √(4kTRB)

Sensitivity Estimate: Sensitivity = System Noise Floor + Required SNR

Frequently Asked Questions (FAQ)

Q1: What is noise floor?
Noise floor is the minimum background noise power in a given bandwidth, usually expressed in dBm.

Q2: Why does bandwidth change noise floor?
Thermal noise power increases with bandwidth, so wider channels have higher total noise.

Q3: What is -174 dBm/Hz?
It is the approximate thermal noise density at 290 K in a 1 Hz bandwidth.

Q4: How does noise figure affect receiver sensitivity?
Noise figure adds receiver noise, raising the effective noise floor and reducing sensitivity.

Q5: Can this be used for spectrum analyzer readings?
Yes, if you enter the correct resolution bandwidth and account for instrument noise figure or preamplifier settings.

Disclaimer: This calculator uses thermal noise equations and ideal noise figure addition. Real noise measurements depend on analyzer settings, detector mode, calibration, impedance, bandwidth definition, and measurement setup.

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