ChemBench

Charles's Law Calculator

Heat it up, it expands.

Initial volume (L)

Initial temperature (K)

Final temperature (K)

Final volume

2.333 L

V₁/T₁ = V₂/T₂

What you entered

Initial volume (L): 2Initial temperature (K): 300Final temperature (K): 350

1
V₂ = V₁T₂ ÷ T₁
(2 × 350) ÷ 300= 2.3333

Result

Final volume: 2.333 L

Heating to 350K expands the gas to 2.333L.

Charles's law: volume against temperature at fixed pressure

V1/T1 = V2/T2, with temperature in kelvin. Double the absolute temperature and the volume doubles.

Initial volume	Initial temperature	New temperature	New volume
1 L	273.15 K (0 C)	546.30 K	2.0000 L
1 L	273.15 K (0 C)	298.15 K (25 C)	1.0915 L
2 L	300 K	600 K	4.0000 L
5 L	273.15 K (0 C)	373.15 K (100 C)	6.8305 L
10 L	298.15 K (25 C)	273.15 K (0 C)	9.1615 L

Kelvin is essential here. Going from 0 C to 25 C expands a gas by 9%, not by an infinite amount, because the ratio is 298.15 to 273.15, not 25 to 0.

Volume and temperature rise together

At constant pressure, a gas's volume is directly proportional to its absolute temperature (in Kelvin) — double the temperature and the volume doubles too.

Why a hot air balloon rises

Heating the air inside a balloon expands its volume (Charles's Law in action), making that air less dense than the surrounding cooler air and generating buoyant lift.

Frequently asked questions

A balloon holds 3.0 L of air at 20°C — what volume will it be at 80°C?

Convert to Kelvin: T1 = 293 K, T2 = 353 K. V2 = V1 × T2/T1 = 3.0 × 353/293 = 3.61 L.

Why do I need to use Kelvin and not Celsius?

Charles's law requires an absolute temperature scale. At 0°C the formula would predict zero volume, which is physically wrong. Kelvin starts at absolute zero, so the direct proportionality V/T = constant holds correctly.

How is Charles's law different from Gay-Lussac's law?

Charles's law relates volume and temperature at constant pressure. Gay-Lussac's law relates pressure and temperature at constant volume. Both are special cases of the ideal gas law — use Gay-Lussac's calculator for sealed rigid containers.