ISO 6578:2017规定了将测量时条件下的液化石油气（LPG）和液化天然气（LNG）体积转换为标准条件下的等效液体或蒸汽体积（即15°C和101325 kPaA）或等效质量或能量（热量含量）的计算程序。它适用于储存在储罐中或从储罐中转移到储罐中的冷冻碳氢化合物液体的数量，并在静态储存条件下进行测量。加压气体的计算不在ISO 6578:2017的范围内。

ISO 6578:2017 specifies the calculation procedure to convert the volume of liquefied petroleum gas (LPG) and liquefied natural gas (LNG) under the conditions at the time of measurement to the equivalent volume of liquid or vapour at the standard condition, i.e. 15 °C and 101,325 kPaA, or to the equivalent mass or energy (calorific content). It applies to the quantities of refrigerated hydrocarbon liquids stored in or transferred to/from tanks and measured under static storage conditions. Calculation of pressurized gases is out of the scope of ISO 6578:2017.