What is the standard pressure setting for altimeters at sea level?

The standard pressure setting for altimeters at sea level is 29.92 inches of mercury (inHg). This value, known as the standard atmospheric pressure, is used universally in aviation to ensure that all aircraft are referencing the same base pressure when measuring altitude.

The significance of this standard lies in its role in providing a uniform reference for all pilots and air traffic control. By using a common pressure setting, it reduces the risk of altitude discrepancies between different aircraft, which is critical for maintaining safe separation in the airspace system.

The choice of 29.92 inHg is based on the average atmospheric pressure at sea level under standard conditions, known as "standard temperature and pressure" (STP). Understanding this standard is essential for pilots when calibrating their altimeters before flight, particularly when flying at high altitudes or transitioning between different pressure systems.