How to Calculate the distance with the rssi value and tx power??

[vprasath]

How to calculate the Distance between the central and peripheral where the peripheral is transmitting power at -40 dBm and my rssi value is -100 dBm ?

I'm using the nRF52 DK!!

[AmbystomaLabs]

As awneil pointed out it is difficult. Due to the difficulty there are many, many propagtion models and indeed entire companies devoted to mapping all the trees, buildings, rocks and hills on the planet just so wireless services can be deployed with some confidence as to their performance.

But if you are dealing with a sparse forest, loose brush or an otherwise generally clear area between transmitter and receiver it can become somewhat accurate. Under these circumstances an accuracy of 90% is feasible.

The ITU is one of the more respected resources for propagation models. Here is a link to one of their publications: www.itu.int/.../R-REC-P.1411-6-201202-S!!PDF-E.pdf

If you are looking for a single use approach there are many online calculators. Though most are structured with the loss number as the output: www.everythingrf.com/.../free-space-path-loss-calculator