In this study, a geographic information system (GIS)-based model was developed to calculate the post-earthquake ignition probability of a building, considering damage to the building's interior gas and electrical distribution system and the overturning of appliances. In order to make our model more reliable and realistic, a weighting factor was used to define the possible existence of each appliance or other contents in the given occupancy. A questionnaire was prepared to weigh the relevance of the different components of post-earthquake ignitions using the analytical hierarchy process (AHP). The questionnaire was evaluated by researchers who were experienced in earthquake engineering and post-earthquake fires. The developed model was implemented to HAZTURK's (Hazards Turkey) earthquake loss assessment software, as developed by the Mid-America Earthquake Center with the help of Istanbul Technical University. The developed post-earthquake ignition tool was applied to Kucukcekmece, Istanbul, in Turkey. The results were evaluated according to structure types, occupancy types, the number of storeys, building codes and specified districts. The evaluated results support the theory that post-earthquake ignition probability is inversely proportional to the number of storeys and the construction year, depending upon the building code.