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 torr?
A torr is a pressure unit equal to approximately 1/760 of an atmosphere. It is used in vacuum technology, low-pressure experimental physics, and blood pressure measurement in older clinical literature.
Real-world uses
Torr is used in vacuum technology, semiconductor manufacturing, and blood pressure measurement (mmHg ≈ torr). Vacuum chambers for electron beam welding operate at about 10⁻⁵ torr, and freeze-drying processes typically operate at 0.1–1 torr.
History
Named after Evangelista Torricelli, who invented the mercury barometer in 1644. The torr was defined to approximate the pressure exerted by 1 mm of mercury. It was formally standardized as 1/760 of a standard atmosphere.
Common mistakes
Assuming torr and mmHg are exactly the same—they are nearly identical but differ by about 0.000015%. For most purposes they are interchangeable, but ultra-precise vacuum work may require distinction.
When is this conversion used?
Converting between bar and torr 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 = 750.0616827 torr
1 torr = 133.32236842 pascal
How to convert bar to torr
To convert bar to torr, multiply the value by 750.0616827.
To convert torr back to bar, multiply by 0.00133322.
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 torr
| bar | torr |
|---|---|
| 0.1 | 75.00616827 |
| 0.5 | 375.03084135 |
| 1 | 750.0616827 |
| 2 | 1,500.12336541 |
| 5 | 3,750.30841352 |
| 10 | 7,500.61682704 |
| 25 | 18,751.5420676 |
| 50 | 37,503.0841352 |
| 100 | 75,006.16827039 |
| 250 | 187,515.42067598 |
| 500 | 375,030.84135195 |
| 1,000 | 750,061.6827039 |
Common values
| bar | torr | |
|---|---|---|
| Car tyre | 2.2 bar | 1,650.13570195 torr |
| Standard atmosphere | 1.01325 bar | 760 torr |
| Blood pressure (systolic) | 0.16 bar | 120.00986923 torr |
| Deep-sea submersible | 1,100 bar | 825,067.85097429 torr |
| Bicycle tyre | 6.2 bar | 4,650.38243276 torr |