Talking about pressure, it means a force which is acting on a specified area. Measurement of pressure can be done with a wide variety of units, among which Torr and atm are the two basic units implemented in the process of calculating pressure.

Torr which has a symbol of ‘Torr’, is a unit implemented for the measurement of pressure based on an absolute scale. Torr is now defined with an exact value of 1/760 belonging to a standard atmosphere (101325 Pa). Hence, one torr is exactly 101325/760 Pascals.

History speaks that one torr was intended to be equal to one “millimeter of mercury”. Howsoever, parallel redefinitions of these units have made them slightly different. The torr is not acceptable officially by the International System of Units (SI), but is frequently with the metric prefix milli with the name of millitorr or 0.001 Torr. This unit was named after the Italian physicist and mathematician, Evangelista Torricelli.

The standard atmosphere is a unit of pressure defined as 101325 Pa (1.01325 bar). It is often used as a reference to standard pressure. It is approximately equal to the atmospheric pressure that is present in the sea level. This originally defines the pressure exerted by 760 mm of mercury at 0°C. It was used as a reference condition to the physical and chemical properties, and was implicit regarding the definition of Centigrade.

There exists two simple ways for the conversion of Torr to atm. Since, 1 atm = 760 Torr, on dividing the atm by 760 the result is always in Torr.

Alternately, we can find how many atm’s are in 1 Torr by dividing 1 atm by 760 Torr, to get 0.001316. Hence, 1 Torr = 0.001316 atm. Torr is simply multiplied by 0.001316 to find atm.  The formula for converting torr to atm is,

Atm = Torr/760.
Atm = Torr x 0.001316

For example, torr is converted into atm,

Find 100,000 Torr in atm
100,000 (0.001316) = 131.578947
100,000 Torr – 131.578947 atm.

Alternately, Torr can be divided by 760 to get a value in atm (Torr/760 = atm).

For example, find 3 atm in Torr.

3 atm * 760 = 2280 Torr. 

Neither the Torr nor the atm is an SI unit of pressure. The SI unit using which the pressure is calculated is Pascal, which carries a definition saying, pressure equals to 1 newton of force per 1 square meter. Both torr and atm can be again converted to Pascal.

Examples:

1.Convert 3265.7 Torr to atm.
3265.7 Torr/760 = 4.3 atm.
2.  Convert 2644.8 Torr into atm.
2644.8/760 = 3.48 atm.

With these two simple examples we can certainly determine a few things of how the conversion of Torr from atm works. The best method that includes the conversion of Torr into atm is mentioned above with the examples. When Torr is to be converted into atm, it is divided by 760 to get hold of the value in atm. This process can be stated as the fastest way of converting torr into atm.