Pressure Converter
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Understanding Pressure Units
What is Pressure?
Pressure is the force applied perpendicular to a surface per unit area. It's measured as force divided by area (P = F/A). Pressure is essential in physics, engineering, meteorology, and everyday applications like tire inflation and blood pressure.
Common Pressure Units
Pascal (Pa)
The SI unit of pressure. One pascal equals one newton per square meter. Named after Blaise Pascal.
Bar
Equal to 100,000 pascals. Commonly used in meteorology and industrial applications. Close to 1 atmosphere.
PSI (lb/in²)
Pounds per square inch. Common in the US for tire pressure, hydraulics, and gas cylinders.
Atmosphere (atm)
Standard atmospheric pressure at sea level. 1 atm = 101,325 Pa = 14.7 PSI.
Medical Pressure Units
mmHg (Torr)
Millimeters of mercury. Used for blood pressure readings. Normal BP is about 120/80 mmHg.
inHg
Inches of mercury. Used in US weather reports for barometric pressure. Standard is ~29.92 inHg.
Common Pressure Values
| Application | PSI | Bar | kPa |
|---|---|---|---|
| Atmospheric pressure | 14.7 | 1.01 | 101.3 |
| Car tire (passenger) | 30-35 | 2.1-2.4 | 210-240 |
| Bicycle tire (road) | 80-130 | 5.5-9 | 550-900 |
| Scuba tank | 3,000 | 207 | 20,700 |
| Home water pressure | 40-80 | 2.8-5.5 | 280-550 |
Conversion Formulas
PSI = bar × 14.504
bar = PSI × 0.0689
kPa = PSI × 6.895
atm = PSI ÷ 14.696
Gauge vs Absolute Pressure
Gauge pressure (PSIG) measures relative to atmospheric pressure.Absolute pressure (PSIA) includes atmospheric pressure. A tire at 30 PSIG is actually at about 44.7 PSIA. Most everyday measurements use gauge pressure.
Frequently Asked Questions
How do I convert PSI to bar?
Multiply PSI by 0.0689 to get bar. For example, 30 PSI × 0.0689 = 2.07 bar. To convert bar to PSI, multiply by 14.504. A quick approximation: 1 bar ≈ 14.5 PSI.
What is standard atmospheric pressure?
Standard atmospheric pressure at sea level is defined as 1 atmosphere (atm), which equals 101,325 pascals, 1.01325 bar, 14.696 PSI, or 760 mmHg. This is the pressure exerted by Earth's atmosphere under standard conditions.
What's the difference between gauge and absolute pressure?
Gauge pressure (PSIG) measures pressure relative to atmospheric pressure—your tire gauge reads 0 when open to air. Absolute pressure (PSIA) includes atmospheric pressure. A tire at 32 PSIG is actually at about 46.7 PSIA (32 + 14.7 atmospheric).
Why is blood pressure measured in mmHg?
Blood pressure uses millimeters of mercury (mmHg) because early instruments were mercury manometers. The height of mercury in a tube indicated pressure. Normal blood pressure is 120/80 mmHg (systolic/diastolic). This equals about 16/10.7 kPa, but mmHg remains the medical standard.