The integrating pressure-and-temperature instrument registers, on a counter, the total quantity of gas passed through the meter, reduced to standard cubic feet at a definite base pressure and base temperature. Each increment of volume is multiplied by a temperature-factor corresponding to the line-temperature and base-temperature. It is then multiplied by the pressure-multiplier corresponding to the line pressure and base pressure. The product is totaled on a counter index. A supplementary index is furnished which reads the total quantity passed at line conditions.