What happens to a gas when it expands through a regulator, is compressed, or sits in a cylinder in the sun? This calculator uses real-gas properties from CoolProp, an open-source property library, and runs in your browser. Pick the gas, the process and the starting conditions, and it gives the final temperature or pressure next to what the ideal gas law predicts.
The second part works out how much gas a cylinder really holds: free gas, mass and Z-factor. It shows how far real gases at cylinder pressures stray from the ideal-gas formulas.