Ideal Gas Law Calculator

The ideal gas law, PV = nRT, connects pressure, volume, amount of gas, and absolute temperature. It combines several simpler gas relationships into one equation: pressure rises when gas is compressed, volume expands with temperature, and more moles mean more particles contributing to pressure.

The constant R depends on the units used. Temperature must be absolute, usually Kelvin, because gas volume and molecular kinetic energy relate to distance above absolute zero rather than Celsius or Fahrenheit offsets. Unit consistency is not a detail; it is part of the law.

The ideal gas model imagines particles moving randomly, colliding elastically, and occupying negligible volume compared with the container. Pressure comes from countless molecular impacts on container walls. Temperature reflects average kinetic energy.

This microscopic view explains the macroscopic equation. Raising temperature increases particle speeds and therefore pressure if volume is fixed. Increasing volume gives particles more space, reducing collision frequency with the walls. Adding moles adds more particles and raises pressure if volume and temperature stay constant.

Many gases behave approximately ideally at low pressure and high temperature, where particles are far apart and intermolecular forces are relatively small. Air near room conditions is often close enough for practical estimates.

The model becomes weaker at high pressure, low temperature, or near phase changes. Real molecules have volume and attractions. In those situations, equations such as van der Waals or compressibility-factor corrections may be needed. Ideal gas results are a baseline, not a universal truth.

The ideal gas law appears in chemistry stoichiometry, ventilation, cylinders, balloons, engines, weather, lab experiments, and safety calculations. It can estimate gas amount from pressure and volume or predict how pressure changes with temperature.

Care is especially important with sealed containers. Heating a fixed-volume gas raises pressure, sometimes dangerously. Gas calculations should respect rated equipment limits, material compatibility, and real-gas behavior when conditions are extreme.