Partial Pressure Calculator

Summary

Calculate partial pressure of any gas in a mixture using Dalton's Law — enter mole fractions and total pressure, or work backwards from partial pressure.

How it works

1. Enter the total pressure of the gas mixture and choose the pressure unit (atm, kPa, Pa, mmHg, bar, or psi).
2. Add each gas component by typing its name and mole fraction (0 to 1). Mole fractions must sum to 1.
3. Click "Calculate" to compute the partial pressure for every gas using P_i = x_i × P_total.
4. The results table shows each gas's mole fraction, partial pressure, and percentage contribution.
5. Use the "Solve for Total Pressure" mode to find P_total when you know one partial pressure and its mole fraction.
6. Click Reset to clear all fields and start a new calculation.

Use cases

• Determine the partial pressure of oxygen in air at a given atmospheric pressure.
• Calculate partial pressures of gas components in industrial process streams.
• Solve chemistry homework and exam problems involving Dalton's Law.
• Find the partial pressure of water vapor in humid air from its mole fraction.
• Verify gas mixture compositions in laboratory or engineering settings.
• Determine the total pressure needed to achieve a target partial pressure.
• Analyze respiratory gas mixtures for medical and diving applications.
• Prepare for AP Chemistry, university general chemistry, or standardized science exams.

Frequently Asked Questions