text: Charles's Law states that the volume of a given amount of dry ideal gas is directly proportional to the Kelvin Temperature provided the amount of gas and the pressure remain fixed.\n\nV1 / T1 = V2 / T2\n\nWhen the three parameters, temperature, volume and pressure are not constant, you can use the relatio P1V1/T1=P2V2/T2 Whenever either of the parameters is constant, just cancel it out and you can get the relationship between the remaining variables.