The pressure of a gas can be measured in various units. Here are some of the most common units used to measure gas pressure:

• Pascal (Pa) or kilopascal (kPa): This is the standard SI unit for pressure. At a standard temperature of 0 ℃ or 273 K, pressure is measured as one atmosphere (1 atm), which is equivalent to 101,325 Pa or 101.3 kPa/05%3A_Gases_and_the_Kinetic-Molecular_Theory/5.02%3A_Gas_Pressure_and_Its_Measurement).

• Atmosphere (atm): This is another unit of pressure that is commonly used. At standard temperature and pressure, one atmosphere is equivalent to 101,325 Pa or 1.01 × 10⁵ Pa/05%3A_Gases_and_the_Kinetic-Molecular_Theory/5.02%3A_Gas_Pressure_and_Its_Measurement).

• Millimeters of mercury (mmHg) or torr: This unit of pressure is based on Evangelista Torricellis work. At sea level, 1 atm of air pressure will sustain a column of mercury at 760 mm, meaning 1 atm = 760 mmHg or 760 torr. The "torr" is an absolute scale pressure measurement that is equal to precisely 1/760 of a standard atmosphere.

• Pounds per square inch (psi): This unit of pressure is commonly used in the United States. At standard temperature and pressure, one atmosphere is equivalent to approximately 14.7 psi.

These units can be interconverted using the following relations:

• 1 atm = 101,325 Pa = 101.3 kPa = 760 mmHg = 760 torr = 14.7 psi/05%3A_Gases_and_the_Kinetic-Molecular_Theory/5.02%3A_Gas_Pressure_and_Its_Measurement).