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Ideal Gas Law Calculator

Ideal Gas Law Calculator

Enter any three of P, V, n, T. Leave the unknown blank — we’ll solve it instantly.

Decimals:
3
Additional parameters
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How the Ideal Gas Law calculator works

Provide any three variables and leave the fourth blank. The app converts all inputs to SI units — pressure in pascals (Pa), volume in cubic meters (m³), temperature in kelvins (K), amount in moles (mol) — then applies PV = nRT with R = 8.314462618 J·mol⁻¹·K⁻¹. The result is converted back to your chosen unit and rounded to your selected decimal places.

What is an ideal gas?

An ideal gas is a model where particles are point-like with no intermolecular forces. Many real gases behave approximately ideally at moderate temperatures and low pressures.

Ideal gas law equation

PV = nRT. Rearrangements: P = nRT/V, V = nRT/P, n = PV/(RT), T = PV/(nR). Always use absolute temperature (kelvins).

Ideal gas constant

This tool uses the SI value R = 8.314462618 Pa·m³·mol⁻¹·K⁻¹. Unit conversion lets you work with kPa, atm, bar, psi, L, mL, and more.

Frequently Asked Questions

What is an ideal gas?
An ideal gas is a simplified model where particles have negligible volume and experience no intermolecular forces. Under many everyday conditions (low pressure, moderate temperature), real gases behave nearly ideally and follow PV = nRT.
What is the ideal gas law equation?
The ideal gas law is PV = nRT, where P is pressure, V is volume, n is the amount of substance (moles), T is absolute temperature in kelvins, and R is the universal gas constant (8.314462618 J⋅mol⁻¹⋅K⁻¹).
What value of the ideal gas constant does this calculator use?
This calculator uses R = 8.314462618 J/(mol·K), which is equivalent to Pa·m³/(mol·K). All inputs are converted to SI units internally so you can use any supported pressure, volume, and temperature units.
When can I use the ideal gas law?
Use the ideal gas law when the gas is not at very high pressure or very low temperature and does not strongly deviate from ideal behavior. For extreme conditions or highly polar gases, real-gas equations of state usually give better results.
How do I calculate any one of P, V, n, or T?
Start from PV = nRT and rearrange: P = nRT/V, V = nRT/P, n = PV/(RT), or T = PV/(nR). Enter any three known values in the calculator, leave the unknown blank, and it will solve for the fourth automatically.
What is the pressure of 0.1 moles of a gas at 50 °C in a cubic meter?
Using P = nRT/V with n = 0.1 mol, T = 323.15 K, V = 1 m³, and R = 8.314462618, the pressure is P ≈ 268.68 Pa (≈0.269 kPa or 0.00265 atm). You can reproduce this by setting n = 0.1 mol, V = 1 m³, T = 50 °C and leaving P blank.
What gas laws are embedded in the ideal gas law?
PV = nRT contains several classic gas laws as special cases: Boyle’s law (P ∝ 1/V at constant n,T), Charles’s law (V ∝ T at constant n,P), Gay-Lussac’s law (P ∝ T at constant n,V), and Avogadro’s law (V ∝ n at constant P,T).
How do I calculate temperature from moles, volume, and pressure?
Rearrange the ideal gas law to T = PV/(nR). Convert your inputs to consistent units (e.g., Pa, m³, mol), compute T in kelvins, and then convert to °C or °F if needed. The calculator handles the unit conversions automatically.