How to Use the Boiling Point by Altitude Calculator
Water begins to boil the moment its vapor pressure equals the surrounding atmospheric pressure. At sea level (0m elevation), atmospheric pressure is about 1013hPa, and water boils at exactly 100°C. As altitude increases, the air thins and atmospheric pressure drops, so water's vapor pressure reaches that lower pressure at a lower temperature - meaning it starts boiling below 100°C. At 2,000m, for example, atmospheric pressure drops to about 795hPa and water boils at roughly 93°C.
This calculator uses the International Standard Atmosphere (ISA) barometric formula to find the atmospheric pressure at a given altitude, then applies the Antoine equation to calculate water's boiling point at that pressure. It's a handy way to understand why food can end up undercooked at high altitude even though the water boils "easily."
For example, water boils at about 91°C atop Mount Baekdu (roughly 2,750m), about 83°C at Everest Base Camp (roughly 5,364m), and about 71°C at the summit of Everest (roughly 8,849m). When cooking at altitude, it's best to extend cook times or use a pressure cooker. Enter an altitude to instantly see the atmospheric pressure and boiling point.
Frequently Asked Questions
Water boils when its vapor pressure equals the surrounding atmospheric pressure. As altitude increases, atmospheric pressure drops, so water's vapor pressure reaches that lower pressure at a lower temperature - meaning it boils below 100°C.
When water boils at a lower temperature, it transfers less heat energy to food, slowing down cooking. At 3,000m, for example, water boils at about 90°C, so cooking for the same time as at sea level can leave food undercooked - you'll need longer cook times or a pressure cooker.