The ideal gas law, PV = nRT, relates the pressure, volume, amount, and temperature of an ideal gas through the universal gas constant R (8.314 J·mol⁻¹·K⁻¹). This calculator lets you solve for any one of the four variables given the other three, with flexible unit support for each quantity. Pressure can be entered in atm, Pa, kPa, bar, mmHg, or psi; volume in litres, millilitres, cubic metres, or cubic centimetres; and temperature in Kelvin, Celsius, or Fahrenheit. All inputs are converted to SI units internally before solving. The ideal gas law is fundamental to physical chemistry, chemical engineering, and thermodynamics, and is commonly applied in problems involving gas stoichiometry, container design, and atmospheric science.