How ideal gas law calculator works
The ideal gas law packs four centuries of gas experiments into one equation: PV = nRT. Pressure times volume equals the amount of gas (in moles) times the gas constant R = 8.314 J/(mol·K) times absolute temperature. Each of Boyle’s law (P ∝ 1/V at fixed T), Charles’s law (V ∝ T at fixed P) and Avogadro’s law (V ∝ n at fixed P, T) is the special case where the other variables are held still.
Enter any three of pressure, volume, amount and temperature, leave the unknown blank, and the tool solves for it. Every field has its own unit menu: pressure in kPa, atm, Pa, bar, mmHg/Torr or psi; volume in L, mL, cm³ or m³; amount in mol or mmol; temperature in K, °C or °F. Internally everything is converted to SI (Pa, m³, mol, K) — the only system in which R = 8.314 is valid — and the answer is converted back to the units you chose.
The temperature field deserves one warning: the ideal gas law needs absolute temperature. A reading in °C or °F is converted to kelvin first, so 0 °C becomes 273.15 K, not zero. Doubling a Celsius temperature does not double the pressure — doubling the kelvin temperature does. The tool rejects temperatures at or below absolute zero because no real gas can go there.