1 atü - Atmosphärenüberdruck is the pressure expressed in decimal fractions of 1 atmosphere by which a given body of gas or air exceeds ...:t;.he pressure of the atmosphere. Since at sea level the pressure of the atmosphere is approximately 14.7. psi, atü always equals 14.7 psi plus the given decimal fraction. 1,5 atu thus is equal to 14.7 plus 1.5 times 14.7 or 36.75 psi. Normal automobile tire pressures today run from about 0,6 atü or 23.5 psi to about 1,2 atü or 32.3 psi. A conversion formula: (1 + N). To convert psi to atü: (N psi - 14.7) divided by 14.7 - atü.