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Partial Pressure Calculator (Dalton’s Law)
Enter the partial pressure of each gas in a mixture to find the total pressure and each gas’s share of the mixture using Dalton’s Law.
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What This Calculator Does
This tool applies Dalton’s Law of Partial Pressures to a gas mixture. It adds up the partial pressures of up to three gases to find the total pressure of the mixture, and shows what percentage of that total each gas contributes.
The Formula
Dalton’s Law states that the total pressure of a mixture of non-reacting gases equals the sum of each gas’s partial pressure: Ptotal = P1 + P2 + P3 + … Because pressure is proportional to the number of moles at constant temperature and volume, each gas’s percentage of the total pressure also equals its mole percent in the mixture.
A Few Notes
- Leave a gas’s partial pressure at 0 if your mixture only has two components.
- All pressures should be entered in the same unit (this tool uses atmospheres, atm).
- This calculator is for general chemistry education and planning purposes and assumes ideal, non-reacting gas behavior.
Last reviewed August 2026