Boiling Point Calculator
Water's boiling point at altitude, from the pressure.
Water's boiling point at altitude, from the pressure.
Boiling point (°C)
100
212 °F · 101.325 kPa
Water boils when its vapour pressure matches the air above it, so lower pressure means a lower boiling point. This uses the Clausius-Clapeyron relation against the standard atmosphere rather than the "1 °C per 285 m" rule of thumb, which is a linearisation that drifts at altitude. The cooking factor is a rough guide from the rule that reaction rates roughly double every 10 °C — it is why Denver needs longer for eggs and why pressure cookers exist.
How the Boiling Point Calculator works
Water boils when its vapour pressure matches the air above it, so lower pressure means a lower boiling point. This uses the Clausius-Clapeyron relation against the standard atmosphere rather than the familiar 1 °C per 285 m rule, which is a linearisation that drifts at altitude.
Also known as: boiling point at altitude · water boiling point by elevation · high altitude cooking calculator · boiling point by pressure
Where to go next
The Boiling Point question rarely arrives on its own. These are the ones that usually come with it:
- Ideal Gas Law Calculator — PV = nRT, solving for whichever term is missing.
- Pressure Calculator — From a force on an area, or from a depth of fluid.
- Vapor Pressure Calculator — Antoine constants are inputs, because ranges matter.
- Speed Distance Time Calculator — Any one of the three from the other two, in four units.
Frequently asked questions
At what temperature does water boil at altitude?
About 95 °C in Denver at 1,609 m, and near 71 °C on Everest. The drop accelerates with height as the air thins.
Why does food take longer to cook at altitude?
Because the water is cooler, not because it boils more slowly. Reaction rates roughly double every 10 °C, so cooking at 95 °C rather than 100 °C takes noticeably longer.
How does a pressure cooker help?
By raising the pressure above the surrounding air, which raises the boiling point above 100 °C. That is the same mechanism working in reverse.
Does the rule of 1 °C per 285 m work?
Roughly, near sea level. It is a straight-line approximation to a curve, so it drifts at height, which is why this page computes from the pressure instead.
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Related calculators
Ideal Gas Law Calculator
PV = nRT, solving for whichever term is missing.
OpenPressure Calculator
From a force on an area, or from a depth of fluid.
OpenVapor Pressure Calculator
Antoine constants are inputs, because ranges matter.
OpenSpeed Distance Time Calculator
Any one of the three from the other two, in four units.
Open