Convert between pressure units
Standard atmospheric pressure at sea level: 101,325 Pa = 1.01325 bar = 14.696 psi = 760 mmHg = 29.92 inHg = 1 atm. Weather reports often use millibars (1013.25 mb) or hectopascals (1013.25 hPa).
US: psi (pounds per square inch), typically 30-35 psi for cars. Europe/Asia: bar or kPa. 1 bar ≈ 14.5 psi. Many tire gauges show both. Check your vehicle's recommended pressure on the door sticker.
Gauge pressure is relative to atmospheric pressure (reads 0 in open air). Absolute pressure includes atmospheric pressure. Tire at 30 psig (gauge) = about 44.7 psia (absolute). Add 14.7 psi to convert.
Blood pressure uses mmHg (millimeters of mercury), e.g., 120/80 mmHg. The numbers represent systolic/diastolic pressure. This unit persists from historical mercury sphygmomanometers, though digital devices are now common.
A Pascal is 1 Newton per square meter—the SI unit of pressure. It's small (atmospheric pressure = 101,325 Pa), so kilopascals (kPa) and megapascals (MPa) are more practical for most applications.
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