Pressure units measure the force applied over a specific area. Common units include Pascals (Pa), which is the SI unit, and atmospheres (atm), where 1 atm is the average atmospheric pressure at sea level. Other units include bar, psi (pounds per square inch), and mmHg (millimeters of mercury), often used in various scientific and engineering contexts. Different applications may require different pressure units. For example, tire pressure is commonly measured in psi, while blood pressure is often expressed in mmHg. Understanding these units is essential for accurate measurements in fields like meteorology, engineering, and medicine.