This research aimed to study the distance between the transmitter and the receiver on wireless Internet access inside the building using ESP8266EX module. This module measured the Received Signal Strength Indication (RSSI) from 3 access points. The signal propagation path was compared with the calculated Euclidean Distance at the coordinates of the module and access points on the building scale. The comparison between RSSI and calculated Euclidean Distance indicated acceptable result. Thus, RSSI can be used for evaluating distances between modules. However, there were some discrepancies caused by obstructions inside the building that made a multi-directional signal propagation path then fluctuate occurrence each on the measurement of the module.