Boiling Point at Pressure Calculator
Estimate a solvent's boiling point under vacuum, or its vapor pressure at a given temperature, using the Antoine equation. Pick a solvent and enter the value you know.
Calculate
mmHg
Boiling point34.1 °C
How it works
Under reduced pressure a liquid boils at a lower temperature, which is why rotary evaporators and vacuum distillation let you remove solvents gently without overheating a sample. This calculator uses the Antoine equation, log₁₀(P) = A − B/(C + T), with published coefficients for each solvent to relate pressure and boiling temperature.
Switch modes to either find the boiling point at a chosen pressure (in mmHg) or the vapor pressure at a chosen temperature (in °C). The coefficients are valid over each solvent's usual working range; results near the extremes are approximate.
Examples
- Water boils at about 100 °C at 760 mmHg, but near 34 °C at 40 mmHg.
- Lower pressure means a lower, gentler boiling point.
- Switch modes to get vapor pressure from a temperature instead.
Frequently asked questions
- Why does pressure change the boiling point?
- A liquid boils when its vapor pressure equals the surrounding pressure. Lower the pressure and that happens at a lower temperature.
- What is the Antoine equation?
- An empirical relation, log₁₀(P) = A − B/(C + T), linking a solvent's vapor pressure and temperature using three fitted constants.
- How accurate is it?
- Very good within each solvent's fitted range; near the extremes of that range the estimate drifts, so treat edge cases as approximate.
- What units are used?
- Pressure in mmHg (torr) and temperature in °C. 1 mmHg ≈ 1.333 mbar if you need to convert from a vacuum gauge.