Charles's Law Calculator

Charles's Law states that at constant pressure the volume of a fixed amount of gas is directly proportional to its absolute temperature. Written as a proportion between two states it becomes V1/T1 = V2/T2, so if you double the absolute temperature you double the volume.

The proportion only holds on an absolute scale where zero means no thermal energy. This tool converts Celsius entries to Kelvin by adding 273.15, does the math, and converts the answer back to the unit you selected, so you never have to convert by hand.

Any unit you like, such as litres, millilitres, or cubic metres, because only the ratio V2/V1 enters the equation. The one rule is that V1 and V2 must share the same unit, and the result comes back in that same unit.

Exactly three of the four. The 'Solve for' dropdown marks the fourth as unknown and disables its input, and from any three known values the missing one is fully determined.

It is treated as 300.15 K internally, not 300 K. That 0.15 offset is why solving V2 from V1 = 2, T1 = 27 C, T2 = 327 C returns 3.999 rather than an exact 4; the ratio 600.15 over 300.15 is fractionally below 2.

Results are rounded to six decimal places to avoid long floating-point tails. Values that land on a whole number, such as V2 = 4 or T2 = 450, display without decimals.

That is physically impossible, so the calculator rejects any temperature that is zero Kelvin or below, whether you typed it directly or it was produced by the solve. In Celsius that means anything at or below -273.15 degrees is refused.

No. Both V1 and V2 must be greater than zero, since a real gas sample occupies some space. Entering a non-positive volume produces an error instead of a result.

No. The whole calculation runs locally in your browser using a pure function, so nothing you type is uploaded. If you need it in code, the same engine is available through the tool's JSON API.