Pressure
P = nRT / VLast updated:
Ideal Gas Law Calculator
Solve ideal gas law problems for pressure, volume, temperature, or moles. PV=nRT calculator with unit conversions. Free chemistry and physics calculator.
Ideal Gas Law Calculator
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Calculate using PV = nRT
PV = nRT
R = 8.314 J/(mol·K)
Enter values above to see results.
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Physical Chemistry Foundation
Ideal Gas Law Calculator: PV = nRT Guide
Solve for pressure, volume, temperature, or moles in ideal gas systems for process screening and education.
Core Law
PV = nRT
Gas Constant R
8.314 J/(mol·K)
Temperature
Kelvin required
Pressure
Absolute only
Reviewed by: CalculatorApp Chemistry & Engineering Team
What Is the Ideal Gas Law?
PV = nRT combines Boyle's, Charles's, and Avogadro's gas laws into a single equation modeling the behavior of gases under a wide range of practical conditions. Engineers and chemists use it for process vessel sizing, pneumatic system design, and lab calculations where high accuracy close to phase transitions is not required.
Volume
V = nRT / PTemperature
T = PV / nRMoles
n = PV / RT| Gas Type | Ideal Gas Accuracy | Typical Use |
|---|---|---|
| Diatomic (N₂, O₂, H₂) | High at normal conditions | Pneumatics, air storage |
| Noble gases (Ar, He) | Very high | Lab reference, shielding gas |
| CO₂ | Moderate | Carbonation, fire suppression |
| Steam / near-critical | Low | Use steam tables for accuracy |
History Timeline
1662: Boyle establishes pressure-volume inverse relationship.
1787: Charles derives volume-temperature proportionality.
1802: Gay-Lussac formalizes pressure-temperature relationship.
1811: Avogadro proposes equal volumes contain equal moles.
1834: Clapeyron unifies these laws into PV = nRT.
1873: Van der Waals introduces real gas corrections.
PubMed Gas Physiology
Respiratory and gas exchange research database.
WHO Air Quality
Global air quality and indoor gas exposure standards.
CDC NIOSH Gas Hazards
Industrial gas exposure limits and controls.
NEJM Archive
Clinical reference for respiratory and gas-related studies.
Myth: Celsius temperature can be used directly.
Fact: Absolute Kelvin temperature is always required in PV = nRT.
Myth: Gauge pressure is acceptable in the formula.
Fact: Absolute pressure (gauge + atmospheric) must be used.
Myth: Ideal gas works for all industrial gases.
Fact: High-pressure and condensable gases need real gas corrections.
Myth: Ideal gas law works identically for all conditions.
Fact: Accuracy decreases near phase transition or extreme pressures.
FAQ (12)
What is the ideal gas law?
PV = nRT relates pressure, volume, moles, and temperature for ideal gases under reasonable conditions.
What is R in the equation?
R is the universal gas constant: 8.314 J/(mol·K). It relates macroscopic and molecular gas behavior.
When does ideal gas law work well?
It works well at low pressures and high temperatures where intermolecular forces and molecular volume are negligible.
When does it fail?
At high pressures or near condensation points, real gas equations like van der Waals are more accurate.
How do I convert temperature?
Always use absolute temperature (Kelvin). Add 273.15 to Celsius values before using in PV = nRT.
What is molar volume at STP?
At standard temperature (0°C) and pressure (101.325 kPa), one mole of an ideal gas occupies 22.414 L.
Can this apply to gas mixtures?
Yes. Dalton's Law allows the ideal gas law to apply to mixtures using partial pressures.
How do I find moles from mass?
Divide mass by molar mass of the compound (n = m / M) to get moles before using this calculator.
What are common industrial uses?
Gas storage sizing, pneumatics, chemical process design, and HVAC volume calculations.
Why is temperature so critical?
Pressure and volume are highly sensitive to temperature changes; always verify temperature assumptions.
Can I use gauge pressure?
No. Always use absolute pressure (add atmospheric pressure to gauge readings).
Is this suitable for steam or near-critical gases?
No. Use steam tables or real gas equations for high-accuracy work near critical points.
References
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