The instrument that measures air pressure is a barometer. In weather and science, air pressure is often reported in hectopascals (hPa) , millibars (mb) , inches of mercury (inHg) , or millimeters of mercury (mmHg).

Quick Scoop

A barometer is the standard tool for measuring atmospheric pressure, and common versions include mercury barometers and aneroid barometers. Meteorologists use these measurements to track weather changes because falling or rising pressure can signal shifts in conditions.

If you want, I can also explain how a barometer works in one minute.