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Partial Pressure Calculator

Work out partial pressure instantly with clear inputs, formula shown and shareable results.

About Partial Pressure Calculator

In an ideal mixture each gas exerts pressure in proportion to its share of the molecules, so the partial pressure is the mole fraction times the total pressure. One mole of a component in four moles of mixture at 2 atm contributes 0.5 atm. Because mole fraction equals volume fraction for ideal gases, the same number describes the composition by volume.

Formulas

Partial pressure

p(i) = x(i) x P(total)

Mole fraction

x(i) = moles of component / total moles

Worked example

With the default values below, Partial Pressure Calculator returns Partial Pressure Of The Component of 0.5000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total pressure of the mixtureminimum 0 atm
2 atm
Moles of the componentminimum 0 mol
1 mol
Total moles in the mixtureminimum 0 mol
4 mol

Results

Partial Pressure Of The Component
0.5000 atm
Mole Fraction
0.2500
Share By Volume
25.00%
Pressure From Everything Else
1.5000 atm

Step by step

  1. 1Values used
  2. 2Partial pressure
  3. 3Mole fraction
  4. 4Partial Pressure Of The Component= 0.5000 atm
  5. 5Mole Fraction= 0.2500
  6. 6Share By Volume= 25.00
  7. 7Pressure From Everything Else= 1.5000 atm

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is mole fraction the same as volume fraction?

For ideal gases, yes. That is why atmospheric oxygen is quoted as 21% by volume and also has a mole fraction of 0.21.

Does this apply to dissolved gases?

Not directly - use Henry's law for solubility. But the partial pressure computed here is the driving pressure that Henry's law needs.

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