Ideal Gas Law Calculator

The ideal gas law, PV = nRT, links a gas's pressure, volume, amount, and absolute temperature through a single constant of proportionality, R. This calculator uses R = 0.08206 L·atm/(mol·K), which is why pressure defaults to atmospheres and volume to liters — plug in values in those units and the algebra falls out directly by rearranging the equation for whichever variable you select to solve for, with the other three treated as known inputs. Alongside the solved variable, the calculator reports the same pressure in kilopascals and the same temperature in Celsius purely as unit conversions for convenience, not as independent calculations.

It also reports a "molar density" (moles per liter, n/V) rather than a true mass density in grams per liter — going from moles to mass would require the gas's molar weight, which isn't collected as an input, so don't confuse this figure with the density you'd measure on a gas of known identity. The isothermal curve chart plots pressure against volume from 1 to 50 liters while holding moles and temperature fixed at whatever values you entered (or computed), tracing the classic inverse P-V relationship at constant T. The biggest limitation to keep in mind: the ideal gas law assumes point-mass molecules with no intermolecular attraction, which breaks down at high pressure or low temperature where real gases condense or deviate significantly — this calculator won't warn you when you've entered conditions far outside where the ideal approximation actually holds.