The ideal gas law (PV = nRT) is the fundamental equation relating pressure, volume, temperature, and amount of gas. It combines Boyle's, Charles's, and Avogadro's laws into one powerful formula.
PV = nRT
Pressure × Volume = Moles × Gas Constant × Temperature
Units: atm, Pa, kPa, mmHg, torr
Standard: 1 atm = 101.325 kPa = 760 mmHg
Units: L (liters), m³, mL
Standard: 22.4 L at STP for 1 mole of gas
Units: mol
Find from: n = mass / molar mass
Values depend on units:
Units: Kelvin (K) — MUST use Kelvin!
Conversion: K = °C + 273.15
⚠️ Never use Celsius or Fahrenheit in this formula
P = nRT / V
V = nRT / P
n = PV / RT
T = PV / nR
PV = nRT → V = nRT / P
V = (2.0 mol × 0.08206 L·atm/(mol·K) × 298 K) / 1.0 atm
V = 48.9 L
Answer: 48.9 L
ALWAYS convert to Kelvin! K = °C + 273.15. This is the #1 mistake.
If P is in atm and V in L, use R = 0.08206 L·atm/(mol·K). Match your R to your units!
n is moles, not grams. Use n = mass / molar mass first.
PV = nRT relates pressure, volume, moles, and temperature for ideal gases. It assumes gas particles don't interact and have no volume.
Works best at low pressure and high temperature. Real gases deviate at high pressure or low temperature.
R = 0.08206 L·atm/(mol·K) for atm and liters. Use R = 8.314 J/(mol·K) for SI units. Match R to your pressure and volume units.
STP = Standard Temperature and Pressure = 0°C (273 K) and 1 atm. At STP, 1 mole of gas = 22.4 L.
Reviewed for accuracy by Muhammad Zohaib, MSc Chemistry
All formulas verified against academic standards • Editorial Policy