Ideal Gas Law Calculator
Calculate pressure, volume, amount or temperature for an ideal gas using PV = nRT.
How to use the ideal gas law calculator
- Choose which quantity you want to solve for (pressure, volume, amount, or temperature).
- Enter the three other known quantities.
- The selected quantity is calculated automatically.
What is the ideal gas law?
The ideal gas law PV = nRT describes the relationship between pressure (P), volume (V), amount of substance in moles (n) and temperature (T) for an ideal gas, where R is the universal gas constant (8.314 J/(mol·K)). The law is a good approximation for most gases under normal pressures and temperatures.
Frequently asked questions
Why must temperature be in kelvin?
Because the gas law is built on an absolute temperature scale where 0 represents the absence of thermal motion. Celsius has an arbitrary zero point (water's freezing point), which would give incorrect results in the formula.
What is the gas constant R?
R = 8.314 J/(mol·K) is the universal gas constant, which links pressure, volume, amount and temperature for all ideal gases regardless of which gas it is.
When is a gas not "ideal"?
At very high pressure or very low temperature (near the condensation point), the molecules' own volume and the attractive forces between them start to matter, and the gas deviates from ideal behavior. Under normal conditions (room temperature, atmospheric pressure), the approximation is very good for most gases.