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Pressure Unit Quick Reference by Field
- Physics / Science: Pascal (Pa), kilopascal (kPa), atmosphere (atm)
- Meteorology: Millibar (mbar), hectopascal (hPa) — numerically identical
- Medicine: mmHg (blood pressure), cmH₂O (respiratory)
- US Engineering / Automotive: PSI (pounds per square inch)
- European Engineering: Bar, millibar
- Hydraulics: PSI (US), bar or MPa (international)
- Vacuum systems: Torr, mbar, Pa (absolute pressure)
- Diving: Atmospheres (atm), bar
Examples
Example 1: Atmospheric Pressure Reference Values
Standard Atmospheric Pressure (1 atm) in all units:
101,325 Pa (pascals)
101.325 kPa (kilopascals)
1.01325 bar
1013.25 mbar (millibars / hectopascals)
1 atm (atmospheres)
14.696 psi (pounds per square inch)
760 mmHg (millimeters of mercury)
760 torr
29.921 inHg (inches of mercury)
1.0332 kgf/cm² (kilograms-force per square centimeter)
Example 2: Tire Pressure Conversion (PSI to Bar and kPa)
Typical car tire pressure: 32 PSI
32 PSI → Bar: 32 × 0.0689476 = 2.21 bar
32 PSI → kPa: 32 × 6.89476 = 220.6 kPa
Common tire pressures:
28 PSI = 1.93 bar = 193 kPa (underinflated)
32 PSI = 2.21 bar = 220 kPa (typical car)
35 PSI = 2.41 bar = 241 kPa (SUV/truck)
80 PSI = 5.52 bar = 552 kPa (road bicycle)
110 PSI = 7.58 bar = 758 kPa (racing bicycle)
Note: European tire gauges use bar; US gauges use PSI.
Example 3: Blood Pressure (mmHg)
Blood pressure reading: 120/80 mmHg
Systolic (120 mmHg):
120 mmHg = 15,999 Pa = 16.0 kPa = 1.74 PSI
Diastolic (80 mmHg):
80 mmHg = 10,666 Pa = 10.7 kPa = 1.16 PSI
Blood pressure categories (mmHg):
Normal: < 120 / < 80
Elevated: 120-129 / < 80
High Stage 1: 130-139 / 80-89
High Stage 2: ≥ 140 / ≥ 90
Crisis: > 180 / > 120
Medical pressure measurements always use mmHg (or torr,
which is numerically identical to mmHg).