About the Boiling Point at Altitude Calculator
Water boils when its vapour pressure equals the pressure of the air above it. Climb a mountain and the air pressure drops, so water boils at a lower temperature. This boiling point at altitude calculator estimates the air pressure at your elevation using the standard atmosphere, then finds the temperature at which water reaches that vapour pressure using the Antoine equation.
It is handy for cooks and bakers who live at altitude (pasta, eggs, beans and rice all take longer when water boils cooler), for campers and hikers planning fuel and water purification, for home brewers and candy makers, and for science students studying phase changes. You can also enter a barometric pressure directly, for example from a weather station or a pressure-cooker gauge (absolute pressure).
Expect roughly a 1 °F drop in boiling point for every 500 ft of elevation, or about 1 °C per 300 m. The altitude option assumes average (standard-atmosphere) weather; a passing high- or low-pressure system can shift the real boiling point by about 1 °F. Results are for pure water — dissolved salt or sugar raises the boiling point slightly.
How to use the boiling point at altitude calculator
- 1Choose whether to calculate from elevation or from air pressure.
- 2Enter your elevation in feet or metres (or the absolute pressure and its unit).
- 3Pick whether to see °F or °C first.
- 4Read the boiling point, the air pressure and how much cooler it is than at sea level.
Formula and method
First the air pressure at elevation h (in metres) comes from the International Standard Atmosphere troposphere formula, which assumes sea-level pressure of 101,325 Pa and a temperature that falls 6.5 °C per kilometre. If you enter a pressure directly, that step is skipped.
Then the Antoine equation for water is solved for temperature. Below one atmosphere the coefficients A = 8.07131, B = 1730.63, C = 233.426 (pressure in mmHg, temperature in °C, fitted for 1–100 °C) are used; above one atmosphere the set A = 8.14019, B = 1810.94, C = 244.485 (99–374 °C) is used. The result matches steam tables to within a few tenths of a degree in the range people cook and live in.
- h
- Elevation above sea level (m)
- p
- Absolute air pressure (Pa; mmHg in the Antoine equation)
- T_b
- Boiling point of water (°C)
- A, B, C
- Antoine coefficients for water
Worked examples
Denver, Colorado (5,280 ft)
At one mile up the standard air pressure is about 83.4 kPa (24.6 inHg). Water reaches that vapour pressure at about 94.7 °C, or 202.4 °F — roughly 9.6 °F cooler than at sea level.
La Paz, Bolivia (3,640 m)
The standard atmosphere gives 64.6 kPa at 3,640 m, so water boils at about 87.9 °C (190.2 °F). Cooking pasta or beans takes noticeably longer there.
Summit of Mount Everest (8,849 m)
Standard pressure at the summit is about 31.4 kPa, under a third of sea level, giving a boiling point near 70 °C. Measured summit pressure is usually a little higher (about 33–34 kPa), so the real figure is closer to 71 °C.
Using a barometer reading of 70 kPa
With an absolute pressure of 70 kPa (similar to about 10,000 ft), the Antoine equation gives a boiling point of about 90.0 °C, or 194.0 °F.
Frequently asked questions
Why does water boil at a lower temperature at high altitude?+
Water boils when its vapour pressure matches the surrounding air pressure. Air pressure falls as you climb, so water reaches that point at a lower temperature — about 202 °F in Denver instead of 212 °F at sea level.
How much does the boiling point drop per 1,000 feet?+
Roughly 1.8–2 °F per 1,000 ft (about 1 °C per 300 m) in the elevations where people live. The drop is slightly smaller per foot at higher elevations because pressure falls off exponentially.
Does food cook faster or slower at altitude?+
Slower when boiling or simmering, because the water is cooler. Pasta, rice, beans and hard-boiled eggs need extra time, and recipes for candy, jam and baking often need adjusting for the lower boiling point.
Is boiling water at altitude still safe for drinking?+
Yes. The CDC recommends a rolling boil for 1 minute, or 3 minutes above 6,500 ft (about 2,000 m), to make up for the lower boiling temperature when disinfecting water.
How does a pressure cooker change the boiling point?+
It traps steam to raise the internal pressure, typically about 100 kPa (15 psi) above atmospheric. At roughly 2 atmospheres absolute, water boils near 120 °C (248 °F), which cooks food much faster.