This all-in-one online Ideal Gas Law Calculator performs calculations using the ideal gas law formula that relates the values of pressure, volume and temperature of a given amount of an ideal gas. You can enter the values of any three parameters in the fields of the calculator and find the missing parameter.
PV = nRT
Ideal Gas Law
The ideal gas law, also known as the general gas equation, is the equation of state of a hypothetical ideal gas. It relates the pressure, volume and temperature of a fixed mass of a gas that is close to an ideal gas. The law was first stated by Benoît Paul Émile Clapeyron as a combination of the already known empirical gas laws: Boyle’s law, Charles’s law, Avogadro’s law, and Gay-Lussac’s law.
The ideal gas law is commonly written in the following empirical form:
$$PV = nRT,$$
where
• \(P \ \) is the pressure of the gas,
• \(V \ \) is the volume of the gas,
• \(n \ \) is the amount of substance of gas (measured in moles),
• \(R \ \) is the ideal, or universal, gas constant,
• \(T \ \) is the temperature of the gas (measured in Kelvins).
It should be emphasized that the above formula uses temperature measured in Kelvin. Recall that the Kelvin is the SI unit for temperature and is sometimes referred to as absolute temperature. If you want to use other temperature units, you must use the following conversion formulas:
$$Celsius = Kelvin \ – \ 273.15,$$
$$Fahrenheit = \frac{9}{5} \cdot Celsius + 32.$$
These conversions are done automatically when you use our ideal gas law calculator and select the units you need.
When using the ideal gas law, remember that it only applies to gases that are close to an ideal gas. An ideal gas consists of particles of negligibly small size that do not interact with each other. The ideal gas model makes it easy to understand the physical meaning of the ideal gas law.
Intuitively, an increase in gas temperature causes individual gas molecules to move faster. The faster the molecules move, the more often and with greater force they collide with the walls of the gas container. More frequent and forceful collisions result in higher pressure, provided the volume of the container remains constant. However, if the volume of the container is adjustable and the external pressure constant, the volume of the gas will increase while the pressure remains the same.
On the other hand, an increase in the gas volume causes an increase in the average path length of the gas molecule before it collides with the wall of the gas container. This leads to less frequent collisions and, as a result, to a lower gas pressure, provided the gas temperature (and hence the average speed of the molecule) remains constant.
The reverse processes occur when the parameters change in the opposite direction. As can be seen from the above formula, when the temperature decreases to zero, the pressure and volume of the gas also tend to zero. The temperature of 0 K = -273.15 ºC is called absolute zero. According to classical physics, at this temperature all motion ceases, therefore the pressure vanishes and the size-less particles do not occupy any volume.
Related calculators
Check out our other physics calculators such as Boyle’s Law Calculator or Gay-Lussac’s Law Calculator.