Absolute pressure is calculated from a vacuum (0 PSI) and atmospheric pressure is14.7PSIa or 14.7 PSI above a vacuum 1PSI on a tire pressure gauge is called 1PSIg = 15.7PSIa 10PSIg=24.7PSIa 100PSIg=114.7PSIa etc.
Absolute pressure is calculated from a vacuum (0 PSI) and atmospheric pressure is14.7PSIa or 14.7 PSI above a vacuum 1PSI on a tire pressure gauge is called 1PSIg = 15.7PSIa 10PSIg=24.7PSIa 100PSIg=114.7PSIa etc.