Ideal Gas Law Calculator

CalculatorApp.me

Part of:Engineering Calculators 2026: Complete Reference for Structural, Electrical, Mechanical, Thermal & Fluid Engineering

Back to Engineering

Ideal Gas Law Calculator

No Intrusive AdsAI-Powered

Calculate using PV = nRT

PV = nRT

R = 8.314 J/(mol·K)

Solve For

Volume

Moles (n)

Temperature

Enter values above to see results.

Want to learn more? Browse our calculation guides and tutorials →

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.

Pressure

P = nRT / V

Volume

V = nRT / P

Temperature

T = PV / nR

Moles

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

Related Calculators

Molar Mass Calculator

Molarity Calculator

Density Calculator

Specific Heat Calculator

Heat Transfer Calculator

Pressure Vessel Calculator

Explore More Chemistry & Gas Tools

Combine gas calculations with molar mass, molarity, and thermal tools for complete process analysis.

Open Engineering Suite

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.

Methodology, sources & limitations

This calculator uses a published formula and the values entered in the calculator to generate the result.

Formula: PV = nRT
Jurisdiction & units: Intended for US, IN, EU, GB, AU, CA, Global. Supports both units where applicable.
Assumptions & limitations: Results are preliminary estimates based on the inputs you provide. Confirm material properties, loads, local codes, and final designs with a qualified professional.
Review status: Formula and automated QA completed June 21, 2026; independent professional review is pending. Next scheduled review: September 21, 2026.

Validation sources

NIST Chemistry WebBook

Ideal Gas Law Calculator — Answer & Method

Calculate pressure, volume, temperature, or moles using PV=nRT.

Formula: Ideal Gas Law

PV = nRT

P = Pressure (atm)

V = Volume (L)

n = Moles (mol)

T = Temperature (K)

Example Calculation

1 mole of ideal gas at STP occupies 22.414 liters.

Important limitation

Check the result against your specific circumstances before making a decision.

Key Facts

The universal gas constant R = 0.08206 L·atm/(mol·K).
At STP (0°C, 1 atm), one mole of ideal gas occupies 22.414 L.

Sources & Validation

NIST Chemistry WebBook

Related Calculators

Molarity Calculator Specific Heat Calculator

Deterministic: YesAI-Generated Numbers: NoVerified: 2026-02-12

Want to learn more? Browse our calculation guides and tutorials →