Abstract: There is no unified LPG metering standard in China, and no basic data sufficient for calculation are available to solve the problem, basic data selected in some codes bublished abroad are introduced to provide parameters and equation for LPG metering. Similar to other oil product metering, it is necessary for the vacumm mass to be converted into atmospheric mass in order to perform the calculation of gas and liquid due to the fact that it is stored in pressurized vessels, for which reason, the mass of the product stored in the tank should be the total sum of liquid mass and that of the saturated gas.In this paper, introduced with emphesis is the method of calculating LPG mass in the light of the measured data about tanks. Calculated out seperately for the LPG both in liquid and gasious phases, the volume, density, standardized volume and the mass in the air. The total sum of liquid phase and that of gas is the mass of LPG. Practical calculation on LPG storage capacity is done based on LPG tanks.