What is standard sea-level atmospheric pressure in hectopascals?

Standard sea-level atmospheric pressure is 1013.25 hPa.

This value is the internationally defined standard atmosphere pressure at mean sea level. It is equivalent to 101,325 pascals, 1,013.25 millibars, or one standard atmosphere. Meteorologists use it as a reference when comparing pressure observations from different places and elevations.

Actual sea-level pressure changes constantly as weather systems move. High-pressure systems generally have greater pressure than the standard value, while low-pressure systems have less. Pressure charts often display these variations with isobars, which connect locations having equal pressure.

Station pressure is the pressure measured at an instrument’s actual elevation. Weather reports commonly reduce that value to mean sea-level pressure so readings from mountains, valleys, and coastal stations can be compared. The standard value is therefore a reference, not a daily global average.