Calculate vapor pressure with Raoult's law
Raoult's law calculator accepts two to twelve liquid components. Enter each name, liquid-phase mole fraction, and pure-component vapor pressure at one shared temperature. The page calculates every partial pressure and adds them to obtain the ideal-solution total vapor pressure.
For a component i, pi = xi pi*. A component with mole fraction 0.6 and pure vapor pressure 3.17 kPa contributes 1.902 kPa. Repeating the multiplication for every component and summing the partial pressures gives the total predicted pressure above the ideal mixture.
Prepare mole fractions and pure vapor pressures
Mole fractions must describe the liquid mixture and total one. A small tolerance accepts ordinary rounded entries and normalizes them for calculation; a larger mismatch is rejected. Component names must be unique so partial pressures cannot be confused or silently combined.
Pure-component vapor pressures must all refer to the same temperature. Keep one pressure unit—kPa, mmHg, bar, or atm—for every row. The calculator does not look up vapor-pressure data or convert values measured at different temperatures into a common condition.
Interpret partial and total vapor pressure
Each partial pressure is the pressure that component contributes in the ideal-vapor description. Total pressure is their sum. Dividing a partial pressure by the total gives the corresponding ideal vapor-phase fraction, which need not equal the liquid mole fraction when pure vapor pressures differ.
A useful check is that each partial pressure cannot exceed its entered pure-component pressure when mole fraction is from zero to one. The total should lie between reasonable combinations of the pure pressures, and a pure-component limit with xi = 1 should recover that component’s pure vapor pressure.
Recognize ideal-solution limitations
The displayed equation is the ideal-mixture form of Raoult's law. Real liquid interactions can produce positive or negative deviations, azeotropes, association, dissociation, or reaction. Gas-phase non-ideality and pressure-dependent fugacity can also matter beyond simple classroom conditions.
Do not use the result as a substitute for measured vapor-liquid equilibrium data when designing distillation, storage, pressure relief, exposure controls, or flammable-material handling. Use citable property data, an appropriate activity-coefficient model, and qualified engineering methods for consequential decisions.
Private data and reproducible results
Copy the row names, mole fractions, pure vapor pressures, temperature source, and pressure unit with any result. Without the shared temperature, the same numbers cannot be reproduced meaningfully. Display precision reflects arithmetic, not the uncertainty of property data or mixture composition.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.