Ideal Gas Law Calculator
Calculate gas properties using PV = nRT. Solve for pressure, volume, moles, or temperature with automatic unit conversion.
Ideal Gas Law Calculator
PV = nRT - Calculate gas properties
Used for density calculation
Pressure
101.38
kPa
State Variables
P
101.38
kPa
V
22.40
L
n
1.0000
mol
T
273.2
K
Gas Density
1.293 kg/m³
Molar Volume
22.40 L/mol
Ideal Gas Law
R = 8.314 J/(mol·K)
How to Use This Calculator
Select which variable to solve for (Pressure, Volume, Moles, or Temperature). The selected variable will be calculated from the other three values.
Choose a common gas from the dropdown to automatically set the molar mass, which is used for density calculations. Or enter a custom molar mass.
The calculator shows all state variables, gas density, and molar volume at your specified conditions. A note indicates whether the ideal gas assumption is reasonable.
Understanding the Ideal Gas Law
Pressure (P) - The force per unit area exerted by the gas molecules. Higher temperatures or more moles in a fixed volume increase pressure.
Volume (V) - The space occupied by the gas. Gases expand to fill their container and compress under pressure.
Amount (n) - The number of moles of gas. One mole contains 6.022 × 10²³ molecules (Avogadro's number).
Temperature (T) - Must be in absolute units (Kelvin) for calculations. Temperature represents the average kinetic energy of gas molecules.
Frequently Asked Questions
What is the ideal gas law?
The ideal gas law (PV = nRT) relates the pressure (P), volume (V), amount of substance (n), and temperature (T) of an ideal gas through the universal gas constant (R = 8.314 J/mol·K). It's fundamental for gas-phase calculations.
When is the ideal gas law accurate?
The ideal gas law is most accurate at low pressures (< 5 atm) and moderate to high temperatures (well above the boiling point). At high pressures or near condensation, real gas equations like van der Waals should be used.
What is the molar volume at STP?
At Standard Temperature and Pressure (0°C, 1 atm), one mole of an ideal gas occupies 22.414 liters. This is a useful reference for gas volume calculations.
How do I calculate gas density from the ideal gas law?
Gas density can be calculated as ρ = PM/(RT), where M is the molar mass. This calculator automatically computes density when you provide the molar mass of your gas.
What is the gas constant R?
The universal gas constant R = 8.314 J/(mol·K) = 8.314 Pa·m³/(mol·K). In other units: R = 0.0821 L·atm/(mol·K) or R = 1.987 cal/(mol·K).
Can I use this for real gases?
This calculator uses the ideal gas law, which is an approximation. For real gases at high pressure or low temperature, the results may deviate. The calculator provides a warning when conditions suggest significant deviation.
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