# Which physical size is measured in Torr?

The bar is a permissible (SI-compliant) unit for pressure in physics and technology. The name comes from the Greek word báros "Weight, pressure" off.

On January 1, 1978, the bar in the Federal Republic of Germany and Austria replaced the unit of measurement physical atmosphere or, for short, atm (the atmosphere) from. The widespread abbreviation atü (atmosphere overpressure) is replaced by "bar overpressure". The actual SI unit for pressure is the pascal (a very small unit). From January 1, 1980, the Pascal was introduced as a unit of measurement for pressure in the GDR and the old units kp / cm², mmWS and at (the atmosphere) or atm were no longer permitted. In accordance with EC Directive 80/181 / EEC, the bar unit may continue to be used (such as the liter, minute or electron volt units). 1 bar is also roughly the pressure by which the hydrostatic pressure increases per 10 meters of water depth.

• 1 bar = 105N / m² = 105 Pa
• 1 mbar = 1 hPa = 100 Pa (read: 1 millibar = 1 hectopascal)
• 1013.25 mbar = 1013.25 hPa = 1 atm (normal pressure)

Differences in the table below of the technical atmosphere at from the standard atmosphere atm.

### Conversion table

Pascalbar technical atmosphere physical atmosphereTorrPounds per square inch
(Pa) (bar) (at) (atm) (torr) (psi)
≡ 1 N / m² ≡ 1 Mdyn / cm² ≡ 1 kp / cm² ≡ pSTP ≡ 1 mmEd ≡ 1 lbf / in.²
1 Pa 1 1,0000 · 10−5 1,0197 · 10−5 9,8692 · 10−6 7,5006 · 10−3 1,4504 · 10−4
1 bar 1,0000 · 105 1 1,0197 · 100 9,8692 · 10−1 7,5006 · 102 1,4504 · 101
1 at 9,8067 · 104 9,8067 · 10−1 1 9,6784 · 10−1 7,3556 · 102 1,4223 · 101
1 atm 1,0133 · 105 1,0133 · 100 1,0332 · 100 1 7,6000 · 102 1,4696 · 101
1 torr 1,3332 · 102 1,3332 · 10−3 1,3595 · 10−3 1,3158 · 10−3 1 1,9328 · 10−2
1 psi 6,8948 · 103 6,8948 · 10−2 7,0307 · 10−2 6,8046 · 10−2 5,1715 · 101 1

Exponential representation rounded to four places.

### Absolute and atmospheric-relative

In everyday use, pressure is often measured with reference to atmospheric pressure. I. E. If someone says that their car tires have a pressure of 2.3 bar, then they are actually 2.3 bar above atmospheric pressure (of approx. 1 bar), i.e. about 3.3 bar absolute. 2.3 bar relative to the atmosphere is approx. 3.3 bar absolute.

In the case of absolute pressure specifications, there is also the notation “bara” 'or “bar (a) or bar abs.” For “bar absolute”.

In the case of relative pressure specifications, there is also the notation bar / g = bar / rel = barg (bar gauge).