What is the atmospheric pressure at sea level on a standard day?

The atmospheric pressure at sea level on a standard day is defined as 29.92 inches of Mercury (inHg) or 1013.2 millibars. This standard value is significant in aviation and meteorology as it serves as a reference point when measuring altitudes and determining aircraft performance.

Using 29.92 inches of Mercury corresponds with the International Standard Atmosphere (ISA), which postulates that at sea level, under standard conditions, this is the expected atmospheric pressure. Additionally, the millibar measurement of 1013.2 is a commonly used unit in weather reporting and helps in understanding pressure systems and their effects on weather patterns.

The other values listed do not represent the standard atmospheric pressure. They may reflect different conditions or altitudes, which is why they are not considered correct in the context of standard atmospheric pressure at sea level.