Thermal Noise Floor Calculator

The tool calculates the thermal noise floor of a radio receiver.

Enter the:

  • Temperature in either Kelvin or Celsius
  • Bandwidth
  • Noise Figure in dB


Noise FloordBm = 10*Log10(kTB/(1 mW)) + NF


  • T = Temperature in Kelvin
  • B = Bandwidth in Hz
  • k = Boltzmann’s constant
  • NF = Noise Figure

Noise Floor of a Radio Receiver

In a radio receiver, the noise floor is the level below which a signal will not be detected. In practice, a signal has to be a few dB higher before it can be detected. This level is called the Minimum Detectable Signal level.

Example Noise Floor Calculation

Let’s calculate the noise floor of a LoRa receiver system.

For a temperature of 25oC, 125 kHz Bandwidth and a noise figure of 10 dB, the noise floor is -113 dBm. Increasing the antenna cable length will directly impact the noise figure and increase the noise floor.