Boiling Point Calculator

Boiling is a condition, not a temperature — it happens where vapour pressure meets the surrounding air.

Water boils at100 °Cat 0 m, where the air is 101.33 kPa

Air pressure there101.325 kPa (760 mmHg)100% of sea level

Below 100 °C by0.0031 °Croughly one degree per 285 metres near sea level, and the rate steepens as you climb

THE FOOD COOKS SLOWERbecause the water is genuinely coolerboiling is not a temperature, it is a condition. The water reaches its boiling point and stops heating, and at altitude that point is lower. No amount of extra flame helps

At Denver94.7 °C1,600 m

At Lhasa87.9 °C3,650 m

At Everest base camp82.1 °C5,364 m

At the summit of Everest70.3 °C8,848 m

A pressure cooker reverses itabout 121 °C at 1 bar gaugeraising the pressure raises the boiling point, which is why autoclaves sterilise and why a pressure cooker works at altitude

The formula

log₁₀P = 8.07131 − 1730.63 ÷ (233.426 + T), P in mmHg

Boiling is a condition, not a temperature

A liquid boils when its vapour pressure equals the pressure pressing down on it.

At sea level water reaches 760 mmHg of vapour pressure at 100 °C. Reduce the surrounding pressure and it reaches the new, lower threshold at a lower temperature. Nothing about the water has changed.

Why food takes longer up a mountain

Boiling water at 2,000 metres is genuinely 93 °C rather than 100, and on Everest about 70.

Once water boils it stops getting hotter however much heat you apply, so the food is cooking at a lower temperature. Turning up the flame boils it away faster and cooks nothing quicker. A pressure cooker is the only real answer.

The Antoine equation is empirical

It is a fitted three-parameter curve, not a derivation from first principles.

The constants used here cover roughly 1 to 100 °C for water; outside that range a different set is required, and using these would give a confident wrong answer.

Ideal behaviour is an approximation

The colligative and gas relations here assume dilute solutions and ideal gases, which real systems approach and do not reach.

At high concentration or high pressure the deviations become large, and the corrections are substance-specific. These figures are right where the assumptions hold and approximate where they do not.