Flow calorimeter is a device used to determine the calorific value of a substance with water media as a circulation and heat sink. The working principle of a calorimeter is to know the value of heat transfer of a substance with an intermediary of water so that it can be used to determine the calorific value of the fuel. The fuel used is liquefied petroleum gas (LPG). The purpose of this study is to determine the LPG calorific value theoretically and experimentally so that it can be used as a reference in determining the effect of variations in the flow rate of LPG, water and air on the calorific value and efficiency of the flow calorimeter. This research is a development of previous research, wherein the previous calorimeter uses valve openings on the burner and water discharge as parameters. While for this study using a comparison of the volume flow rate of each of LPG: air, which is 0.2 LPM: 4.8 LPM and 0.3 LPM: 7.2 LPM at 1 LPM water discharge as the parameter. The tool used to determine the discharge is a flow meter tool. Based on the parameters used, it is hoped that LPG calorific value can be identified correctly and can know the efficiency value of the flow calorimeter apparatus accurately. From the results of the study, the lowest experimental calorific value was found in the variation of 0.2 LPM LPG which was 37,990.19 kJ / kg and the highest experimental calorific value was found in the variation of 0.3 LPM LPG which was 38,261.25 kJ / kg. The lowest calorimeter efficiency results were found in 0.3 LPM LPG discharge variation which was equal to 77.8% and the highest flow calorimeter efficiency was found in 0.2 LPM LPG discharge variation which was 78.15%. For theoretical LPG calorific value that is equal to 46,454.31 kJ / kg. It can be concluded that the amount of fuel supply capacity accompanied by the amount of fluid capacity as heat absorbers and the addition of combustion air (excess air) will affect the high and low experimental LPG calorific value and efficiency of the flow calorimeter.