Chemistry

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Partial Pressure Calculator.

Calculate a component partial pressure using Dalton's law.

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Partial pressure: 0.25 pressure units

Partial pressure

0.250000pressure units

Educational arithmetic only. Keep units consistent and use measured or explicitly supplied chemistry inputs; this tool does not infer reaction pathways, property tables, or safety guidance.

Use Cases

Scuba Diving Gas Mixtures

Determine the partial pressure of oxygen or nitrogen in a breathing gas blend to ensure safe exposure at depth.

Example: For air with 21% O2 at 5 atm total pressure, oxygen partial pressure is 1.05 atm.

Industrial Gas Mixing

Calculate the partial pressure of a specific gas in a mixture for process control or quality assurance.

Example: In a 10 atm mixture with 0.3 mole fraction of CO2, its partial pressure is 3 atm.

Frequently Asked Questions

What is Dalton's law of partial pressures?
Dalton's law states that in a mixture of non-reacting gases, the total pressure equals the sum of the partial pressures of each individual gas. The partial pressure of a component is the pressure it would exert if it alone occupied the entire volume.
How do I use this partial pressure calculator?
Enter the mole fraction of the gas component (a value between 0 and 1) and the total pressure of the gas mixture. The calculator multiplies the mole fraction by the total pressure to give the partial pressure, following Dalton's law.
What units can I use for total pressure?
You can use any pressure unit you prefer, such as atm, kPa, mmHg, or psi. The partial pressure result will be in the same unit you entered for total pressure, so ensure consistency.

Tips & Common Mistakes

Tips

  • Ensure the mole fraction is between 0 and 1. If you have a percentage, divide by 100 first.
  • Use consistent pressure units for total pressure and the result; the calculator does not convert units.
  • For ideal gas mixtures, partial pressure is independent of the gas type, only the mole fraction matters.
  • Double-check your mole fraction: it should be the fraction of the component in the gas mixture, not the mass fraction.

Common Mistakes to Avoid

  • Entering a percentage (e.g., 21) instead of a decimal (0.21) for mole fraction.
  • Mixing pressure units, such as entering total pressure in atm but expecting result in kPa.
  • Assuming partial pressure equals mole fraction times total pressure for non-ideal gases; this is an approximation valid for ideal gases.

Last updated: August 13, 2026