Thermodynamics

Vapor Pressure (Antoine) Calculator

Saturation pressure of a pure component from Antoine coefficients. Pick a preset or enter your own A, B, C.

log₁₀(P) = A − B / (C + T)

How it works

The Antoine equation fits a pure component's saturation pressure to three constants (A, B, C) over a stated temperature range. Plug in the temperature and the coefficients for your compound to get the vapor pressure.

Worked example

Water at 25 °C with the standard mmHg/°C coefficients. Returns ≈ 3.17 kPa — the saturation pressure of water at room temperature.

Inputs

• Compound — Presets use mmHg / °C convention.
• Temperature (°C)
• A (custom only)
• B (custom only)
• C (custom only)

Frequently asked questions

What units does the Antoine equation use?

It depends on the coefficient set. The presets here use the classic engineering convention of pressure in mmHg and temperature in °C; the result is then converted to kPa, bar, and psia. Always match your A, B, C to the same convention.

Why is my result wrong outside the temperature range?

Antoine coefficients are fitted to a specific temperature band. Extrapolating beyond that band gives unreliable numbers — use coefficients valid for your temperature, or a different correlation.

Where do I get Antoine coefficients?

The NIST Chemistry WebBook lists them for thousands of compounds, along with the valid temperature range. Verify the units before using them.

Assumptions

• Pure component; no mixture effects.
• Antoine form log10(P[mmHg]) = A − B/(C + T[°C]).

References

• Antoine coefficients: NIST Chemistry WebBook
• Method documented in Perry's Chemical Engineers' Handbook (vapor pressure correlations).

Related Thermodynamics tools

• Ideal Gas Law — Moles, mass, and density of an ideal gas from P, V, and T.
• Gas Compressor Power — Single-stage adiabatic compression power, head, and discharge temperature for an ideal gas.
• Steam Tables (IAPWS-IF97) — Saturated and single-phase water/steam properties — saturation pressure/temperature, enthalpy, entropy, and specific volume — from the IAPWS-IF97 standard.

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