Charles's law states that, at constant presuure, the volume, V, of a given mass of gas is directly proportional to the absolute temperature.

This directly proportional relationship can be written as: $V\propto T\mathrm{or}\frac{V}{T}=k$
where:
V is the volume of the gas.
T is the temperature of the gas (measured in Kelvin).
k is a constant.

Because the formula is equal to a constant, Charles's law can be rewritten as: $\frac{V_1}{T_1}=\frac{V_2}{T_2}$

The law was named after scientist Jacques Charles, who formulated the original law in his unpublished work from the 1780s.

Example:
A gas with a volume of 2 liters at 100 K is heated to 200 K. What is the new volume with no change in pressure?

$\frac{V_1}{T_1}=\frac{V_2}{T_2}$

$V_2=V_{1}x\frac{T_2}{T_1}=3\mathrm{liters}x\frac{200K}{100K}=6\mathrm{liters}$

Charles's law is based upon absolute temperature. The absolute temperature is calculated by adding 273 to the temperature in Celsius scale. 10°C is equiavalent to 283 K.

$T_{}=10\mathrm{°C}+273=283K$