Water Boiling Point by Altitude Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 10/11/2026
Water's boiling point drops with altitude, by about 1°C every 300 m (more precisely 0.003354°C per meter). At 1500 m altitude, water boils at about 95°C instead of 100°C at sea level.
Explanation
Water starts boiling when its vapor pressure equals the surrounding atmospheric pressure: at sea level, this equality happens at 100°C, but atmospheric pressure decreases with altitude, which mechanically lowers the temperature needed to reach that equality. This phenomenon, often underestimated, has a direct and sometimes frustrating culinary consequence at altitude: water boils "more easily" (at a lower temperature), but that lower temperature transfers less energy to food per unit of time, which noticeably lengthens cooking times for boiled foods (pasta, legumes, eggs, vegetables) compared to a recipe designed at sea level. The approximation used here, a linear drop of about 0.003354°C per meter (roughly 1°C every 300 m), is a practical simplification of a relationship that's actually nonlinear, combining the barometric formula (pressure as a function of altitude) and the Clausius-Clapeyron equation (boiling temperature as a function of pressure): this linear approximation stays reliable for everyday cooking use up to fairly high mountain altitudes, but gradually departs from exact values beyond that. This calculator gives only the boiling point itself, not an adjusted cooking time: the relationship between a temperature drop and an increase in cooking time varies too much by food and preparation to be reduced to a single reliable universal formula.
Example: a mountain town at 1500 m altitude
Inputs
Altitude: 1500 m.
Calculation
Boiling point = 100 − 1500 × 0.003354 = 100 − 5.025 ≈ 94.97°C.
Result
At 1500 m altitude, water boils at about 95°C, 5°C lower than at sea level.
Frequently asked questions
Why does boiled food cook more slowly at altitude?
Because water boils at a lower temperature, heat transfer to food immersed in that water is slower than at 100°C: even though the water visually boils the same way (bubbling), it's simply less hot. To compensate, high-altitude cooking recipes generally recommend lengthening the cooking time rather than trying to raise the temperature, since the water physically cannot exceed its boiling point at that altitude.
Is this linear formula accurate at very high altitude?
No, it's a practical approximation of a relationship that's actually nonlinear. It stays reasonably reliable up to common mountain altitudes, but gradually departs from the exact value at very high altitude (for example, high mountains above 4000-5000 m): an accurate calculation at those altitudes would require the full barometric formula combined with the Clausius-Clapeyron equation rather than this linear approximation.
Does this temperature drop also affect oven baking?
No, not directly: an electric or gas oven heats by radiation and air convection, independent of water's boiling point. Altitude does affect other aspects of high-altitude baking, however (lower atmospheric pressure makes dough rise faster and more strongly, often requiring adjusted yeast or baking powder amounts), a phenomenon distinct from the one this calculator addresses.