How this calculator works
Air pressure drops as altitude increases because there's less atmosphere pressing down from above — this calculator uses the International Standard Atmosphere (ISA) model to convert altitude to pressure. Water boils when its vapor pressure matches the surrounding air pressure, so lower air pressure means water boils at a lower temperature; the Antoine equation converts that pressure into a boiling point.
- h — altitude above sea level (m)
- P — air pressure at that altitude (kPa)
- T — water's boiling point at that pressure (°C)
Common values
| Altitude (m) | Water boils at |
|---|---|
| 150 m | 99.5 °C |
| 380 m | 98.7 °C |
| 750 m | 97.5 °C |
| 1,500 m | 95.0 °C |
| 2,300 m | 92.4 °C |
| 3,000 m | 90.0 °C |
| 4,500 m | 85.0 °C |
| 7,500 m | 74.9 °C |
More detail
Why food takes longer to cook at altitude
Cooking relies on heat, not just boiling — but boiling water can't exceed its boiling point no matter how long or hard you heat it. At 1,500 m, water boils at about 95 °C instead of 100 °C, so anything cooked in boiling water (pasta, rice, eggs) is simmering at a lower temperature and needs more time to reach the same doneness. A commonly used rule of thumb is that boiling point drops roughly 1 °C for every 300 m of elevation — this calculator computes the more precise value from the physics directly instead of using that shortcut.
Why pressure cookers matter more at altitude
A pressure cooker raises the internal pressure above ambient, which raises water's boiling point back toward (or above) 100 °C — this is why high-altitude cooking guides often recommend a pressure cooker or longer cook times to compensate for the lower boiling point this calculator shows.
Cooking tip. If a recipe timing assumes sea level and you're cooking above roughly 1,000 m, add extra time for boiled or simmered foods, or increase the heat slightly to compensate — the water simply can't get hotter than its boiling point at your altitude.
Frequently asked questions
At what temperature does water boil on a mountain at 1,500 m?
About 95.0 °C, with air pressure around 84.6 kPa — enter 1500 above to confirm. That's roughly 5 °C below sea-level boiling.
What's the boiling point of water at the summit of Mount Everest (8,848 m)?
About 70.3 °C by the standard-atmosphere model (31.4 kPa); measured summit pressure is higher (~33.7 kPa), putting the real boiling point near 72 °C.
Is the "1 °C per 300 m" rule accurate?
Better than you might expect. Pressure falls off close to exponentially with altitude, but the boiling point falls almost linearly. Across this calculator's whole valid range (0–11,000 m) the rule's largest gap from the computed value is 0.49 °C, at 11,000 m; at the summit of Everest (8,848 m) the rule gives 70.5 °C against a computed 70.3 °C, a gap of 0.24 °C. The real rate steepens only slightly, from about 302 m per °C near sea level to about 288 m per °C near 11,000 m. For comparison, ordinary day-to-day pressure swings move the boiling point by around 1 °C on their own, so the rule of thumb is fine for cooking. This calculator computes the exact curve anyway.
Why does water boil at a lower temperature at altitude?
Water boils when its vapor pressure equals the surrounding air pressure. Air pressure drops with altitude (less atmosphere pushing down), so water needs less added heat energy to reach that matching point — meaning it boils at a lower temperature.