Why is the Kelvin scale used in gas-law calculations?

The Kelvin scale is used in gas-law calculations primarily because it is an absolute temperature scale that sets its zero point at absolute zero.123

Using an absolute scale ensures that temperature values are always non-negative, which is essential for the mathematical validity of gas laws. For instance, Charles’s law states that the volume of a gas is directly proportional to its absolute temperature. If a relative scale like Celsius were used, the mathematical relationship would break down at or below zero degrees, as volume cannot be negative.3451

Furthermore, the ideal gas law was specifically formulated so that it takes a simple mathematical form when absolute temperature is used. Historical choices regarding the definition of the Kelvin scale were made to ensure this simplicity, allowing physical laws and formulas to be expressed more clearly and consistently across scientific measurements.523