Sigfox is a radio protocol Low Power Wide Area Network (LPWAN) technology that has a characteristic global reach, cost-effective, energy efficiency, and simplicity. Sigfox operates in the unlicensed spectrum frequency band, during transmitting and receiving messages, Sigfox uses ultra-narrow band (UNB) modulation technique. This paper analyzes Sigfox based network planning for public Internet of Things (IoT) services in a metropolitan area that has 10.37 million population and 662.3 km2. The result of the study stated that 33 access points are needed to cover the entire city. The simulation result shows that 99.9% of the area has a Reference Signal Received Power (RSRP) Downlink level above -134 dBm. The mean values of RSRP Downlink and Signal to Interference and Noise Ratio (SINR) Downlink are -91.81 dBm and 7.98 dB, respectively. Meanwhile, for the Received Signal Strength Indicator (RSSI) Downlink parameter, 98.7% metropolitan area is covered and has a mean value of -87.91 dBm. Okumura-Hata radio propagation model is used and gives results that allowed propagation loss and shadow fading margin are 152.5 dB and 7.5 dB, respectively, thus cell range for one access point reaches 3.28 km.