Overview

Calculate how the boiling point of water changes with altitude (atmospheric pressure). Useful for cooking at high elevations, laboratory vacuum distillation, and meteorology.

Formula

Clausius-Clapeyron Equation (approximation):
ln(P₂/P₁) = (ΔH_vap/R) × (1/T₁ - 1/T₂)

Pressure vs. altitude approximation:
P = P₀ × (1 - 0.0000225577 × h)^5.25588

P₀ = 101,325 Pa (sea level), h = altitude (m)
ΔH_vap (water) ≈ 40,700 J/mol, R = 8.314 J/(mol·K)

Quick estimate: Boiling point ≈ 100 - (altitude(m)/300) °C

How to Use

1. 1Enter the altitude (m) (e.g., 1,000 m).
2. 2Or enter the current atmospheric pressure (hPa or atm) directly.
3. 3The boiling point of water at that condition is calculated automatically.
4. 4Compare with the standard boiling point (100°C).

Tips

• ✔At sea level, the boiling point is 100°C (212°F) at standard pressure.
• ✔At the summit of Mt. Everest (~8,849 m), water boils at about 70°C (158°F).
• ✔At high altitudes, food cooks poorly due to the lower boiling point — use a pressure cooker.
• ✔Pressure cookers raise internal pressure, increasing the boiling point to approximately 120°C (248°F).

FAQ