Vapor Pressure of Water Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Thermochemical and gas-property calculations are sensitive to temperature, pressure, energy units, and reference conditions. Vapor Pressure of Water Calculator keeps those assumptions explicit so the result can be interpreted on the correct basis.

What this calculator does

The Vapor Pressure of Water Calculator uses Temperature, Pressure — Simplified formula, Pressure — Antoine formula, Pressure — Magnus formula, and Pressure — Tetens formula. With the bundled default scenario, the primary result is shown as “Water vapor pressure” and the displayed value is 2.329575 kPa. Supporting outputs include Simplified, Antoine, Magnus. 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

Begin with the quantities that describe the real sample or system, not with a target answer. The main visible inputs are Temperature, Pressure — Simplified formula, Pressure — Antoine formula, Pressure — Magnus formula, and Pressure — Tetens formula. Choose any method or species selector first, then enter the numerical values in the units shown.

How the calculation works

The page’s calculation model is: Water vapor pressure by five common correlations. It uses only the inputs exposed by the calculator and does not silently infer missing composition, purity, mechanism, or laboratory conditions.

Worked example

For a reproducible worked check, enter Temperature = 20 °C. The calculator returns 2.329575 kPa for “Water vapor pressure”. The same run reports Simplified = 2.338096 kPa; Antoine = 2.329575 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 of Water 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 of Water 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.

A useful way to work with the Vapor Pressure of Water Calculator is to save one baseline calculation and then change a single chemically meaningful variable. That makes trends easier to understand and helps expose unit or sign mistakes before they propagate into later work.