Ideal Gas Law Calculator
PV = nRT, solved for whichever variable you're missing.
The equation
PV = nRT, R = 8.314 L·kPa / (mol·K)
One mole of any ideal gas at 0 °C (273.15 K) and 1 atm occupies 22.4 L, the molar volume every chemistry course leans on. The law bundles Boyle's, Charles's and Avogadro's laws into one line; keep temperature in kelvin or every answer comes out wrong.
When 'ideal' breaks down
The model treats molecules as sizeless points that never attract each other. Real gases agree within about 1% near room conditions, but deviate at high pressure (molecule volume matters), low temperature (attractions matter), and near condensation. That's van der Waals territory; for homework and most engineering estimates at everyday conditions, ideal is exactly right.