Vapor Pressure Calculator

Written by Great Medico

Updated September 25, 2026 •3 min read

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A thermodynamic result is meaningful only when its temperature, pressure, and energy basis are clear. Vapor Pressure Calculator ties the calculation directly to the visible scenario instead of hiding those assumptions.

What this calculator does

The Vapor Pressure Calculator uses Clausius–Clapeyron — Initial temperature, Clausius–Clapeyron — Final temperature, Clausius–Clapeyron — Initial pressure, Clausius–Clapeyron — Final pressure, and Clausius–Clapeyron — Molar enthalpy of vaporization. With the bundled default scenario, the primary result is shown as “Vapor pressure” and the displayed value is 11.272199 kPa. Supporting outputs include Clausius–Clapeyron final pressure, Raoult solution pressure. The answer is tied to the exact fields and calculation branch exposed on this page; it does not invent missing sample composition, laboratory conditions, or reference data.

How to use it

The quickest way to avoid an input error is to verify what each field represents before typing a value. This page primarily uses Clausius–Clapeyron — Initial temperature, Clausius–Clapeyron — Final temperature, Clausius–Clapeyron — Initial pressure, Clausius–Clapeyron — Final pressure, and Clausius–Clapeyron — Molar enthalpy of vaporization. Keep the chemical basis consistent when you substitute your own data.

How the calculation works

This calculator uses a specific chemistry relationship rather than a generic prediction model. In this case, Clausius–Clapeyron and Raoult-law sections on one calculator. The output is therefore reproducible from the visible fields, provided the same units and branch selections are used.

Worked example

For a reproducible worked check, enter Clausius–Clapeyron — Initial temperature = 25 °C; Clausius–Clapeyron — Final temperature = 50 °C; Clausius–Clapeyron — Initial pressure = 3.17 kPa; Clausius–Clapeyron — Molar enthalpy of vaporization = 40.65 kJ/mol; Raoult — Mole fraction of the solvent = 0.8; Raoult — Vapor pressure of the solvent = 3.17 kPa. The calculator returns 11.272199 kPa for “Vapor pressure”. The same run reports Clausius–Clapeyron final pressure = 11.272199 kPa; Raoult solution pressure = 2.536 kPa. This default case is useful for confirming that the expected units, selectors, formula, and sign convention are active before you replace the values with your own data.

How to interpret the result

For Vapor Pressure Calculator, the primary output should be read in context. Thermodynamic outputs are tied to their reference conditions and assumptions. Phase, pressure, temperature scale, ideal-gas behavior, and whether an energy value is molar or mass-specific can materially change interpretation. If the result looks surprising, recheck units, prefixes, signs, chemical formula or species selection, and whether every value belongs to the same sample or condition.

Limitations and practical notes

For Vapor Pressure Calculator, keep this limitation in mind: Thermochemical and gas calculators can rely on idealized or reference-condition relationships. Real-fluid properties, phase transitions, heat losses, and pressure-dependent behavior may require property tables or specialized software.

Use the Vapor Pressure Calculator for realistic chemical scenarios and perform a quick reasonableness check. Calculators keep arithmetic consistent, but they cannot determine whether the entered composition, reaction, or experimental setup is physically sensible.