Bar is a unit of pressure that equals to 100,000 Pascal (Pa.) Pascal is a unit of pressure adopted by the International System of Units (SI). The conversion of pressure to the volume (in liters) can be done using the ideal gas law with the formula V = nRT /P. Abbreviations are "P" is pressure, "V" is volume, "T" stands for temperature, n is number of moles of gas and"R" is the molar gas constant. As an example, calculate the volume (in liters) of 6.2 moles of the oxygen gas that is under the pressure of 5.3 bars at 80 Fahrenheit.
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Find out the value of the molar gas constant "R;" R equals to 8.31447 J/mol x K.

Multiply the pressure in bars by the factor 100,000 to convert it to the Pascal unit. In our example, 5.3 bars equals to 530,000 Pascals (Pa).

Add the value "459.67" to the temperature in Fahrenheit (F), and then multiply by 0.55556 to calculate degrees of Kelvin (K). In our example, the temperature of 80 F converts to 0.55556 x (80 + 459.67) or 299.82 K.

Multiply the temperature (Step 3) by the molar gas constant and the number of moles of gas; then divide the product by the pressure (Step 2) to calculate the volume (in cubic meters). In our example, the volume is 299.82 K x 8.31447(J/mol x K) x 6.2 moles / 530,000 Pa = 0.02916 m^3. Note that the result is rounded to the fifth digital point.

Multiply the volume in cubic meters (Step 4) by 1,000 to calculate liters. In the example, it converts to 29.16 (0.02916 x 1,000) liters.