dopecalc

Ideal Gas Law Calculator

Calculate pressure, volume, moles, or temperature of an ideal gas using PV = nRT. Uses R = 0.082057 L·atm/mol·K.

Enter any three of pressure, volume, moles, or temperature. The calculator solves for the fourth using PV = nRT with R = 0.082057 L·atm/mol·K.

atm
L
mol
K

Kelvin only (K = °C + 273.15)

About this Calculator

Calculate pressure, volume, moles, or temperature of an ideal gas using PV = nRT. Uses R = 0.082057 L·atm/mol·K.

Formula & Calculations

Formula

PV = nRT, where R = 0.082057 L·atm/mol·K
Where:
  • P=Pressure of the gas (atm)
  • V=Volume of the gas (liters)
  • n=Number of moles of gas
  • T=Temperature (Kelvin)
  • R=Universal gas constant = 0.082057 L·atm/mol·K

Assumptions

  • The gas behaves ideally (low pressure, moderate temperature).
  • All variables in the equation are consistent with R = 0.082057 L·atm/mol·K.
  • Provide any three of P, V, n, T to solve for the fourth.

Calculation Examples

Example 1

Inputs:P = 1 atm, V = 22.414 L, n = 1 mol
Result:T = 273.15 K

T = PV / nR = (1 × 22.414) / (1 × 0.082057) = 273.15 K (STP conditions).

Example 2

Inputs:P = 2 atm, V = 10 L, T = 300 K
Result:n = 0.812 mol

n = PV / RT = (2 × 10) / (0.082057 × 300) = 0.812 mol.

Example 3

Inputs:n = 2 mol, V = 5 L, T = 350 K
Result:P = 11.488 atm

P = nRT / V = (2 × 0.082057 × 350) / 5 = 11.488 atm.

Frequently Asked Questions

What is the ideal gas law?

PV = nRT relates the pressure, volume, temperature, and amount of an ideal gas. It combines Boyle's, Charles's, and Avogadro's laws into a single equation.

Why do we use Kelvin for temperature?

The gas law requires absolute temperature because gas behavior is proportional to molecular kinetic energy, which is zero at absolute zero (0 K = -273.15°C). Using Celsius or Fahrenheit gives incorrect results.

What if I have units other than atm and liters?

You'll need to convert your values to atmospheres and liters first, or use an alternative value of R that matches your units.