RSSI Calculation Formula

The Received Signal Strength Indicator (RSSI) is a measure of the power in a received radio signal. It is commonly used in wireless communication systems to evaluate the signal strength of a received signal.

RSSI is usually measured in dBm (decibels relative to one milliwatt).

RSSI Formula

The formula for calculating RSSI typically depends on the specific wireless technology and the implementation by the hardware manufacturer. However, a general approach to calculating RSSI from the received power level can be summarized as follows:

RSSI = 10*log10(PmW)


  • PmW is the power expressed in milliwatt.
  • RSSI is the power expressed in dBm

Here is a simple calculator that converts received signal power in Watt to RSSI

What is dBm?

dBm is a unit of power expressed in deciBels referenced to one milliwatt.

It is commonly used in Radio frequency, Microwave and Optical communication systems as a measure of absolute power. It is used due to the ease of representing both very large and very small values with few digits.

For example 10,000,000,000,000 mW = 1013 mW = 130 dBm

As well, it makes RF budget calculations simpler than with linear values.