Boiling Point at Altitude Calculator
Enter an altitude (or a known atmospheric pressure) to find the exact temperature at which water boils at that elevation. The calculator uses the barometric formula to convert altitude to pressure, then the Antoine equation to convert pressure to boiling point. Switch between metric and imperial units; results update instantly.
Why does water boil at a lower temperature at altitude?
The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. At sea level, the atmospheric pressure is about 101.325 kPa (1013.25 hPa), and water boils at exactly 100 °C (212 °F). At higher altitudes the air column above is shorter and therefore lighter, so atmospheric pressure is lower. Because the water molecules need less energy to overcome the reduced external pressure, they enter the vapor phase at a lower temperature. This is why Denver (1609 m) sees water boil around 94.7 °C, and on Mt Everest water only boils at about 71.8 °C.
How the calculator works: barometric formula and Antoine equation
Two equations underpin this calculator. First, the standard barometric formula converts altitude to atmospheric pressure: P = P0 * (1 - L*h/T0)^(g*M/(R*L)), where P0 = 101325 Pa is sea-level pressure, L = 0.0065 K/m is the temperature lapse rate, T0 = 288.15 K is standard sea-level temperature, g = 9.80665 m/s^2 is gravitational acceleration, M = 0.0289644 kg/mol is the molar mass of air, and R = 8.31446 J/(mol*K) is the universal gas constant. Second, the Antoine equation relates vapor pressure to temperature for water: log10(P) = A - B/(C+T), with NIST constants A=8.07131, B=1730.63, C=233.426 (valid 1-100 °C). The calculator inverts this to find T from P. If you enter a pressure directly instead of an altitude, the barometric step is skipped.
Practical effects on cooking and baking at altitude
Every 300 metres of elevation reduces the boiling point of water by roughly 1 °C (1.8 °F). At moderate altitude (1000-2000 m) this is a noticeable but manageable effect: pasta and rice may need a couple of extra minutes. Above 3000 m the drop exceeds 3 °C and cooking times can increase by 10-25%. Baking is even more sensitive: lower pressure means CO2 leavening gases expand more rapidly, often causing cakes and breads to rise too fast and collapse. Common high-altitude baking adjustments include reducing the baking powder or soda by 1/4-1/3, adding extra flour (1-2 tablespoons per cup), and increasing oven temperature by 15-25 °F to set the structure faster.
Food safety note: boiling does not equal 100 °C at altitude
A common misconception is that "boiling water" is always at 100 °C. At altitude it is not. Pathogens are killed by time at temperature, and guidance like "bring to a rolling boil for 1 minute" assumes sea-level temperatures. The U.S. Centers for Disease Control recommends boiling water for 1 minute at altitudes up to 6562 ft (2000 m), and for 3 minutes at higher elevations, to ensure safe disinfection. For cooking, use a calibrated thermometer to verify the internal temperature of meat, poultry, and other foods rather than relying on visible boiling as a proxy for 100 °C.
Boiling point of water at common altitudes
| Location / Altitude | Altitude (m) | Pressure (hPa) | Boiling point (°C) | Boiling point (°F) |
|---|---|---|---|---|
| Dead Sea, Israel (lowest land) | -430 | 1061 | 101.4 | 214.5 |
| Sea level | 0 | 1013.25 | 100 | 212 |
| Denver, Colorado (USA) | 1609 | 836 | 94.7 | 202.5 |
| Cusco, Peru | 3400 | 665 | 87.8 | 190 |
| Lhasa, Tibet | 3650 | 645 | 86.9 | 188.4 |
| Base Camp, Mt Everest | 5364 | 506 | 82.1 | 179.7 |
| Summit, Mt Kilimanjaro | 5895 | 477 | 80.4 | 176.7 |
| Summit, Mt Everest | 8849 | 314 | 71.8 | 161.2 |
Calculated using the barometric formula and Antoine equation. Sea-level pressure assumed at standard conditions (1013.25 hPa, 15 °C).
Frequently asked questions
What is the boiling point of water at 5000 feet (1524 m)?
At 5000 feet (about 1524 m) the atmospheric pressure is approximately 843 hPa, and water boils at about 94.9 °C (202.8 °F). That is around 5 °C below sea-level boiling, which noticeably extends cooking times for foods simmered in water.
Does altitude affect the boiling point of liquids other than water?
Yes. Every liquid has its own vapor pressure curve, but the principle is the same: lower atmospheric pressure means a lower boiling point. Alcohol (ethanol) boils at 78.4 °C at sea level but lower at altitude. This calculator is specifically calibrated for water using NIST Antoine equation constants.
Why does lower pressure cause a lower boiling point?
A liquid boils when the vapor pressure of its molecules equals the pressure pushing down on the surface. At lower atmospheric pressure the molecules need to generate less vapor pressure to overcome it, which requires less thermal energy, so boiling starts at a lower temperature.
How accurate is this calculator compared to a real measurement?
The barometric formula assumes a standard atmosphere (constant lapse rate, standard sea-level temperature). Real-world pressure varies with weather, humidity, and local conditions. Under standard conditions the formula is accurate to within about 1 hPa up to 11 km, translating to less than 0.3 °C error in boiling point. If you know your actual barometric pressure from a weather station or altimeter, use the "pressure" input mode for a more accurate result.
What is the boiling point of water on top of Mount Everest?
At the summit of Mount Everest (8,849 m / 29,032 ft), atmospheric pressure is approximately 314 hPa, and water boils at about 71.8 °C (161.2 °F). That is more than 28 °C below the sea-level boiling point, which is why cooking food by boiling is extremely difficult and slow at that altitude.
Is it safe to drink water that has been boiled at altitude?
Yes, if you boil it long enough. The CDC recommends 1 minute of vigorous boiling at elevations up to about 2000 m (6500 ft), and 3 minutes above that. The lower boiling temperature still kills the vast majority of pathogens; the extra time compensates for the reduced temperature. Chemical treatment (iodine or chlorine tablets) or filtration with a certified filter are reliable alternatives at very high altitude.