⚗️ Ideal Gas Law Calculator
Solve PV = nRT for Any Variable
Chemistry & Physics Gas Calculations
Ideal Gas Law Calculator (PV=nRT)
Solve for:
📊 Enter Known Values
📊 Calculation Steps
Gas Constant R Values
| Value | Units | Use When |
|---|---|---|
| 8.314 | J/(mol·K) | SI units (Pa, m³) |
| 8.314 | L·kPa/(mol·K) | Pressure in kPa, volume in L |
| 0.08206 | L·atm/(mol·K) | Pressure in atm, volume in L |
| 62.36 | L·mmHg/(mol·K) | Pressure in mmHg, volume in L |
| 1.987 | cal/(mol·K) | Energy in calories |
Ideal Gas Law Formulas
The Ideal Gas Law
P = pressure, V = volume, n = moles, R = gas constant, T = temperature
Solving for Pressure
Solving for Volume
Solving for Moles
Solving for Temperature
Related Gas Laws
| Law | Formula | Constant | Relationship |
|---|---|---|---|
| Boyle's Law | P₁V₁ = P₂V₂ | n, T | P ∝ 1/V |
| Charles's Law | V₁/T₁ = V₂/T₂ | n, P | V ∝ T |
| Gay-Lussac's Law | P₁/T₁ = P₂/T₂ | n, V | P ∝ T |
| Avogadro's Law | V₁/n₁ = V₂/n₂ | P, T | V ∝ n |
| Combined Gas Law | P₁V₁/T₁ = P₂V₂/T₂ | n | All three |
How to Use the Ideal Gas Law
- Identify what to solve for — Select P, V, n, or T from the buttons.
- Enter known values — Input the three known variables with correct units.
- Choose the gas constant — Select R that matches your pressure and volume units.
- Convert temperature to Kelvin — The calculator handles this automatically.
- Read the result — Get your answer with step-by-step breakdown.
Scientific Resources
Frequently Asked Questions
The ideal gas law (PV=nRT) relates pressure (P), volume (V), amount in moles (n), and temperature (T) for an ideal gas. It combines Boyle's, Charles's, and Avogadro's laws into one equation.
R is the universal gas constant. Its value depends on the units used: 8.314 J/(mol·K) for SI units, 0.08206 L·atm/(mol·K) for atm and liters. Match R to your pressure and volume units.
The ideal gas law requires absolute temperature. Kelvin starts at absolute zero (-273.15°C). Using Celsius or Fahrenheit would give wrong results because they have arbitrary zero points.
STP (Standard Temperature and Pressure) is 273.15 K (0°C) and 1 atm. At STP, 1 mole of ideal gas occupies exactly 22.4 liters (molar volume).
The ideal gas law is less accurate at high pressures (molecules closer together), low temperatures (near condensation), and for polar gases. Real gases require the van der Waals equation.
Common conversions: 1 atm = 101.325 kPa = 760 mmHg = 1.01325 bar = 14.696 psi. The calculator handles unit selection automatically.
Ideal gases are theoretical: molecules have no volume and no intermolecular forces. Real gases have molecular volume and attractions. Most gases behave ideally at low pressure and high temperature.
Simply add 273.15: K = °C + 273.15. For example, 25°C = 298.15 K. The calculator converts automatically when you select °C or °F.
Yes! For gas mixtures, use Dalton's Law: total pressure = sum of partial pressures. The ideal gas law applies to each component and the mixture as a whole (using total moles).
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Last Updated: January 2026