# Units of pressure

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## One atmosphere(atm)

The pressure of air that can support 760mmHg column at sea level is called one atmosphere.

It is the force exerted by 760mm or 76cm long column of mercury on an area of 1cm2 at standard temperature (0oC).

### Conversion factors:

• 1 atm = 1.01325 bar.
• 1atm= 101.3 kPa.
• 1atm = 14.696 psi (lbf/in2).
• 1atm = 760 torr.
• 1atm= 1013 mbar.

## Pascal (N/m2)

Since 1 Pa is a small pressure unit, the unit HectoPascal (hPa) is widely used, especially in meteorology. The unit kilopascal (kPa) is commonly used design of technical applications like HVAC systems, piping systems and similar.

### Conversion factors:

• 1 atm=101325 Pa.
• 1 Pascal=1 N/m2.
• 101325 pa=760 torr.
• 100,000 pa = 1 bar.
• HectoPascal = 100 Pascal = 1 millibar.
• 1 kilopascal = 1000 Pascal.
• 101325 pa=14.7 psi.

## Pounds per square inch (lbf/in2)

(Psi) was common in U.K. but has now been replaced in almost every country except in the U.S. by the SI units. Since atmospheric pressure is 14.696 psi .

A column of air on an area of one square inch area from the Earth's surface to the space - weighs 14.696 pounds.

### Conversion factors:

• 1 atm = 14.696 psi.
• 14.696 psi = 760 torr.
• 14.696 psi =101325 Pa.
• 14.696 psi=1013 bar.

## Bar

The bar (bar) is common in the industry. One bar is 100,000 Pa, and for most practical purposes can be approximated to one atmosphere even if

There is 1,000 millibar (mbar) in one bar, a unit common in meteorology.

### Conversion factors:

• 1 Bar = 0.9869 atm.
• 1 millibar = 0.001 bar.
• 1millibar = 0.760 torr.
• 1millibar = 100 Pa.

## Torr

torr (torr) is named after Torricelli and is the pressure produced by a column of mercury 1 mm high - equals to 1 / 760th of an atmosphere.

### Conversion factors:

• 1 atm = 760 torr.
• 760 torr = 14.696 psi.
• 760 torr = 101325 Pa.
• 760 torr =1 millibar. Writer: Waleed Altaf