Enter your gas moles (n₁, n₂, n₃), temperature, and volume into the Dalton's Law of Partial Pressures Calculator to find the total pressure of your gas mixture, along with each gas's partial pressure and the total moles — or switch calculation modes to solve for whichever variable you're missing.
Total Pressure
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Partial Pressure Gas 1
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Partial Pressure Gas 2
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Partial Pressure Gas 3
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Total Moles
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Dalton's law states that the total pressure of a gas mixture equals the sum of the partial pressures of each individual gas. Each gas behaves as if it were alone in the container.
Use the ideal gas law: P₁ = (n₁ × R × T) / V, where n₁ is moles of gas 1, R is the gas constant (0.08206 L·atm/mol·K), T is temperature in Kelvin, and V is volume in liters.
For oxygen in air, multiply the total pressure by oxygen's mole fraction (0.21). For example, at 1 atm total pressure, oxygen's partial pressure is 0.21 atm.
Mole fraction is the ratio of moles of one gas to total moles (x₁ = n₁/ntotal). Partial pressure equals mole fraction times total pressure: P₁ = x₁ × Ptotal.
Dalton's law is most accurate for ideal gases at low pressures and high temperatures, where gas molecules don't interact significantly with each other.
Common conversions: 1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 760 mmHg. Use these factors to convert between different pressure units.
Yes, but you must account for water vapor pressure. The dry gas pressure equals total pressure minus water vapor pressure: Pgas = Ptotal - PH₂O.
Dalton's law applies to any number of gases. Simply sum all individual partial pressures to get the total pressure, regardless of how many gases are present.