Flow calorimeter is a device used to determine the calorific value of a substance with water media as 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 liquified petroleum gas (LPG). This research is a development of previous research, wherein the previous calorimeter uses valve openings on the burner and water discharge as parameters. Whereas for the value or amount of LPG air and gas entering it cannot be measured exactly. This will affect the calculation of the heating value of the substance. While in this follow-up study using a stoichiometric equation with two types of variables, namely the independent variable and the dependent variable. For the independent variable is the ratio of the mass flow rate between LPG, air and water, which is 0.4 LPM: 9.6 LPM: 1 LPM and 0.5 LPM: 12 LPM: 1 LPM. Then for the dependent variable is the LPG heating value and the efficiency of the flow calorimeter. Based on the variables 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 0.5 LPM LPG which was 30,221.18 kJ / kg and the highest experimental calorific value was found in the variation of 0.4 LPM LPG which was 33,103.1 kJ / kg. The lowest calorimeter efficiency results were found in 0.5 LPM LPG discharge variation which was equal to 58.8% and the highest flow calorimeter efficiency was found in 0.4 LPM LPG discharge variation which was 65.6%. 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.