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Welcome to the ConvertNow pressure converter hub. Whether you are a student solving homework, a professional completing a project, or a traveller navigating unfamiliar units, our free pressure conversion tools give you instant, accurate results backed by internationally verified constants.
Pressure measurement started with Torricelli's mercury barometer (1643). The atmosphere (atm), torr (mmHg), and psi (pounds per square inch) emerged from practical engineering. The pascal (Pa) — one newton per square metre — became the SI standard in 1971, though psi and bar remain dominant in industry.
Pressure conversion ensures safety in tyres, boilers, diving, and medicine. A 5 psi under-inflated tyre increases fuel consumption by 3 %. Diving tables use bar/atm for decompression stops; confusion causes decompression sickness.
Mechanics, scuba divers, meteorologists, HVAC engineers, medical professionals, and tyre technicians.
PSI vs bar (1 bar ≈ 14.5 psi). Car tyres display dozens of psi; bicycle tyres use 4–8 bar. Diving computers use bar/atm; weather forecasts use hectopascals (hPa).
| Unit | Symbol | Base Equivalent | Common Use |
|---|---|---|---|
| Pascal | Pa | 1 N/m² | SI |
| Bar | bar | 100,000 Pa | Europe, diving |
| PSI | psi | 6,894.76 Pa | US, automotive |
| Atmosphere | atm | 101,325 Pa | Chemistry |
| Torr | Torr | 133.322 Pa | Vacuum science |
| Common Value | Equals |
|---|---|
| 1 bar | 14.5 psi |
| 1 atm | 101.3 kPa |
| 1 psi | 0.069 bar |
| 1 Torr | 133.3 Pa |
Standard atmospheric pressure is 1 atm = 101,325 Pa = 1,013.25 hPa = 1.01325 bar = 14.696 psi.
Passenger cars typically need 30–35 psi. Check your door-jamb placard for the exact recommendation.
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