https://devzone.nordicsemi.com/f/nordic-q-a/17033/nrf51-dongle-calculate-distancehi I used the nrf51 dongle to receive advertisement packet from other nrf51 dongle. I used this formule, d = 10 ^ ((TxPower - RSSI) / 20) , given from this link forums.estimote.com/.../2858 . Example, txpower = -59, and received rssi is -80. den-USTelligent Community 13Thu, 13 Oct 2016 11:25:29 GMThttps://devzone.nordicsemi.com/thread/65338?ContentTypeID=1Thu, 13 Oct 2016 11:25:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:649f8aa6-a19b-4baa-8f19-955c6a30cca6awneil<p>The post you referred to actually makes this clear:</p> <p><em>This will give you very &quot;jumping&quot; results, coming from the nature of RSSI. RSSI readings are not very stable and highly depend on environment</em></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/65337?ContentTypeID=1Thu, 13 Oct 2016 11:23:22 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6393830e-3d84-4792-b8f5-090de9ff7687awneil<p>Unless everything is very carefully calibrated &amp; controlled, RSSI can only give a very rough estimate of distance at best.</p> <p>You can really only expect a near/far indication.</p><div style="clear:both;"></div>