What is bar?
A bar is a pressure unit approximately equal to standard atmospheric pressure, or 100,000 pascals. It is widely used in meteorology, hydraulics, diving equipment, and industrial pressure gauges.
Real-world uses
Bars are widely used in European tyre pressure specifications, compressed gas cylinder ratings, scuba diving depth gauges, and industrial process controls. Espresso machines operate at 9–15 bar. Atmospheric pressure is approximately 1.013 bar.
History
The bar was introduced by Norwegian meteorologist Vilhelm Bjerknes in 1909, derived from the Greek word "baros" meaning weight. Though not an SI unit, it is widely accepted in industry and was retained in the EU Directive on units of measurement.
Common mistakes
Confusing bar with atm—they are close (1 atm ≈ 1.01325 bar) but not identical. Also, gauge pressure (barg) versus absolute pressure (bara) is often mixed up; gauge pressure reads zero at atmospheric pressure.
What is pound per square inch?
Pound per square inch (psi) is an imperial pressure unit widely used in the United States for tire inflation, hydraulic system pressures, gas cylinder ratings, and plumbing specifications.
Real-world uses
PSI is the standard pressure unit in the United States for tyre inflation (typically 30–35 psi for cars), compressed air tools, hydraulic systems, and water pressure. HVAC systems, fire extinguisher ratings, and pressure cooker specifications use psi in North America.
History
Pounds per square inch emerged naturally from the Imperial/US customary system, combining the pound-force with the square inch. It became the dominant pressure unit in American industry and remains deeply embedded in US engineering standards and building codes.
Common mistakes
Not distinguishing between psi (absolute, psia) and psig (gauge, relative to atmosphere). A tyre reading of 32 psig actually means about 46.7 psia. Also, confusing psi with kPa when using equipment from metric countries.
When is this conversion used?
Converting between bar and pound per square inch is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Tyre pressure gauges, HVAC systems, and industrial equipment may use different pressure units depending on the manufacturer and region. Converting between psi, bar, and kPa is common in automotive and engineering work.
Worked examples
1 bar = 14.50377377 pound per square inch
1 pound per square inch = 6,894.75729317 pascal
How to convert bar to pound per square inch
To convert bar to pound per square inch, multiply the value by 14.50377377.
To convert pound per square inch back to bar, multiply by 0.06894757.
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
Quick reference: bar to pound per square inch
| bar | pound per square inch |
|---|---|
| 0.1 | 1.45037738 |
| 0.5 | 7.25188689 |
| 1 | 14.50377377 |
| 2 | 29.00754755 |
| 5 | 72.51886887 |
| 10 | 145.03773773 |
| 25 | 362.59434433 |
| 50 | 725.18868865 |
| 100 | 1,450.3773773 |
| 250 | 3,625.94344326 |
| 500 | 7,251.88688651 |
| 1,000 | 14,503.77377302 |
Common values
| bar | pound per square inch | |
|---|---|---|
| Car tyre | 2.2 bar | 31.9083023 pound per square inch |
| Standard atmosphere | 1.01325 bar | 14.69594878 pound per square inch |
| Blood pressure (systolic) | 0.16 bar | 2.3206038 pound per square inch |
| Deep-sea submersible | 1,100 bar | 15,954.15115032 pound per square inch |
| Bicycle tyre | 6.2 bar | 89.92339739 pound per square inch |