Boiling Point at Altitude
Approximate water boiling point as a function of elevation.
Overview
The Boiling Point at Altitude calculator estimates the temperature at which water boils given an elevation in metres or feet. As you climb, atmospheric pressure drops, so water boils at a lower temperature — which is why pasta takes longer in Denver than in New Orleans and why high-altitude baking has its own set of rules.
The tool is aimed at hikers planning a backcountry meal, home cooks who've just moved to a mountain town and chemistry students working through the Clausius-Clapeyron relation. It answers long-tail queries like "what temperature does water boil at 10000 feet", "boiling point Denver elevation" and "altitude correction for cooking time".
How it works
The calculator uses a simplified linear approximation derived from the standard atmosphere model: the boiling point of water drops by approximately 1 degree Celsius for every 285 metres (about 935 feet) of elevation gain near sea level. The underlying physics is the Clausius-Clapeyron equation, which describes how vapour pressure varies with temperature.
For elevations between sea level and roughly 4500 metres, the linear approximation is accurate to within half a degree. Above that, the curvature of the vapour-pressure relation becomes noticeable and the simple formula begins to under-estimate the drop. The tool reports the result to one decimal place and notes the approximation regime.
Examples
Sea level (0 m) → 100.0 °C / 212.0 °F
Denver (1609 m) → 94.4 °C / 202.0 °F
Mexico City (2240 m) → 92.1 °C / 197.8 °F
Everest base camp (5364 m) → 82.2 °C / 180.0 °F
FAQ
Why does food cook more slowly at altitude?
Boiling water transfers heat into food through convection and the latent heat of vaporisation. When the water can't get hotter than, say, 92 °C, the food simply has less thermal driving force and takes longer to cook through.
Does this affect baking too?
Yes, but in different ways. Lower atmospheric pressure means leavening gases expand more, so cakes rise faster and can collapse. Most high-altitude recipes reduce leavening, increase flour and increase oven temperature.
Is the formula valid for other liquids?
The 1 °C per 285 m rule is specific to water. Other liquids have their own vapour-pressure curves and will fall at different rates with altitude.
What about pressure cookers?
A pressure cooker raises the boiling point above 100 °C by trapping steam. At altitude it raises it above the lower local boiling point. Pressure cookers are the standard fix for slow cooking in mountain kitchens.
Why is the answer slightly off from what my thermometer reads?
Weather changes local pressure too — a low-pressure system can shift the boiling point by half a degree. The calculator uses the average standard atmosphere.