Gay-Lussac's Law Calculator

Gay-Lussac's law describes how the pressure of a fixed amount of gas changes with absolute temperature when its volume remains constant. The relationship is direct: increasing Kelvin temperature increases pressure by the same proportion, while decreasing temperature lowers pressure. The calculator applies P1 divided by T1 equals P2 divided by T2. Pressure may be entered in pascals, kilopascals, bar, atmospheres, or another unit because the answer uses the same pressure unit as the initial value. Temperature must be expressed on an absolute scale. Kelvin starts at absolute zero, so temperature ratios have physical meaning. Celsius values cannot be substituted directly because zero degrees Celsius does not represent zero thermal energy. Convert Celsius to Kelvin by adding 273.15 before using the calculator. A temperature of 27 degrees Celsius, for example, is 300.15 kelvin. Both temperature entries must use the same absolute scale. The law assumes the gas is sealed in a rigid container, the amount of gas does not change, and gas behavior is close to ideal. Heating makes molecules move faster and strike the container walls more often and with greater momentum. Because the walls cannot expand, those collisions appear as increased pressure. This model is useful for classroom gas-law problems, pressure estimates in sealed vessels, aerosol storage discussions, and basic thermodynamics. Real systems may depart from the prediction at very high pressure, very low temperature, near a phase change, or when the container changes volume. Safety calculations should also account for vessel strength, relief devices, measurement uncertainty, and real-gas properties. This calculator provides a transparent proportional estimate rather than an engineering certification. Check that the chosen initial and final states describe the same gas sample, keep pressure units consistent, and use measured absolute temperatures for the most meaningful result. Record input units and assumptions whenever you share a result so another reader can reproduce the calculation and interpret it correctly.