The Gay-Lussac’s Law Calculator computes one unknown variable in the equation P1/T1=P2/T2P₁/T₁ = P₂/T₂P1​/T1​=P2​/T2​, which describes the direct proportionality between pressure and temperature of a gas at constant volume. By providing three of the four variables, the calculator determines the missing value. This tool is useful for physics students, laboratory experiments, and engineering applications to study how gases behave under temperature changes at constant volume.