Partial Pressure Calculator
Use this partial pressure calculator to switch between Dalton's law, the ideal gas law, and two Henry's law forms without rearranging each equation by hand.
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Run the calculator.
What This Partial Pressure Calculator Helps You Do
This page brings the four Omni-style partial-pressure routes into one place, so you can move between gas mixtures, ideal gas calculations, and dissolved-gas estimates without rebuilding the algebra every time.
That is useful in chemistry classes, gas law homework, and quick lab checks where the main decision is not the arithmetic but choosing the right law for the information you actually have.
How to Calculate Partial Pressure Calculator
- Choose the law: Use Dalton's law for gas mixtures, ideal gas law for a single gas amount, or Henry's law for gases dissolved in liquids.
- Enter values in consistent units: This page assumes pressure in atm, temperature in kelvin, volume in liters, and concentration in mol/L.
- Calculate partial pressure: The calculator applies the selected formula and reports the result with context.
Partial Pressure Calculator Formula
| Variable | Meaning | Unit |
|---|---|---|
| p_i | Partial pressure of the gas | atm |
| x_i | Mole fraction of the gas | unitless |
| P_total | Total mixture pressure | atm |
| n_i | Moles of the chosen gas | mol |
| R | Ideal gas constant | L·atm/(mol·K) |
| T | Absolute temperature | K |
| V | Volume of the gas mixture | L |
Use the worked examples below to check how the formula behaves with real values. If the result looks unexpected, verify the unit assumptions and the meaning of each variable before interpreting the answer.
Worked Examples
- Total pressure: 5.00 atm
- O2 mole fraction: 0.21
Result: O2 partial pressure = 1.05 atm
A gas that makes up 21% of the mixture contributes 21% of the total pressure.
- Moles: 0.50 mol
- Temperature: 300 K
- Volume: 10.0 L
Result: Partial pressure = 1.23 atm
Higher temperature or more moles raise pressure if volume is fixed.
- K_H1: 769.23 L·atm/mol
- Concentration: 0.0020 mol/L
Result: Partial pressure = 1.54 atm
Henry's law links gas above a liquid to the amount dissolved at equilibrium.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| < 1 atm | Low partial pressure | Usually indicates a minor gas fraction or a dilute dissolved gas. |
| 1-5 atm | Moderate partial pressure | Typical of many gas-mixture or lab-scale calculations. |
| > 5 atm | High partial pressure | Check whether ideal or Henry assumptions still fit your conditions. |
Frequently Asked Questions
References
Last reviewed: March 2026