Boiling Point at Altitude Calculator
ChemistryCalculate water boiling point at any altitude from sea level to 8,849 m (Everest). Uses barometric pressure and Clausius-Clapeyron equation for accurate results.
Boiling Point (°C)
93.22
Boiling Point (°F)
199.8
Atmospheric Pressure (mmHg)
596.3
Atmospheric Pressure (kPa)
79.5
What is a BP at Altitude?
The Boiling Point at Altitude Calculator computes the temperature at which water boils at any altitude from sea level to the summit of Mount Everest (8,849 m). It first converts altitude to atmospheric pressure using the barometric formula, then applies the Clausius-Clapeyron equation with water's enthalpy of vaporisation (ΔHvap = 40.7 kJ/mol) to find the boiling point at that reduced pressure.
At sea level (0 m), water boils at 100°C because its vapour pressure equals standard atmospheric pressure (760 mmHg) at that temperature. At altitude, atmospheric pressure decreases exponentially — at 3,500 m (Leh, Ladakh), pressure is about 490 mmHg, and water boils at about 87°C. The 13°C reduction has real consequences: pulses, rice, and pasta cook significantly slower at lower boiling temperatures; medical sterilisation by boiling is unreliable; and tea brewed below 85°C is noticeably weaker.
For the general case of finding a liquid's boiling point at any pressure, use the Boiling Point Calculator. For the related problem of finding vapour pressure at a given temperature, use the Vapor Pressure Calculator. For water specifically at any temperature from 0–374°C, the Vapor Pressure of Water Calculator gives the saturation pressure using the Antoine equation.
How to use this BP at Altitude calculator
- Enter your altitude in metres in the Altitude field. Slide the control from 0 m (sea level) to 8,849 m (Everest summit). Common references: Shimla = 2,205 m; Manali = 2,050 m; Leh = 3,500 m; Darjeeling = 2,050 m; Ooty = 2,240 m.
- Read Boiling Point (°C) — the temperature at which water boils at that altitude under open-air conditions.
- Compare to 100°C: if the boiling point is more than 5°C below 100°C (above ~1,500 m), consider using a pressure cooker for cooking dal, rice, and pulses.
- Note Atmospheric Pressure (mmHg) — subtract from 1520 mmHg (2 atm) to understand how much additional gauge pressure your pressure cooker or autoclave must supply to achieve 121°C sterilisation temperature.
- For other liquids, take the computed pressure in mmHg to the Boiling Point Calculator and enter it as the target pressure with your liquid's ΔHvap.
Formula & Methodology
Step 1 — Barometric formula:P = P₀ × (1 − 2.2557 × 10⁻⁵ × h)^5.25588 P₀ = 101,325 Pa, h = altitude in metresStep 2 — Clausius-Clapeyron (solved for T₂):1/T₂ = 1/T₁ − (R / ΔHvap) × ln(P / P₁) T₂ = 1 / [1/T₁ − (R / ΔHvap) × ln(P / P₁)]Where: T₁ = 373.15 K (100°C), P₁ = 101,325 Pa, ΔHvap = 40,700 J/mol, R = 8.314 J/(mol·K) Worked example — Leh, Ladakh (3,500 m):P = 101325 × (1 − 2.2557×10⁻⁵ × 3500)^5.256 = 101325 × (0.9210)^5.256 = 101325 × 0.644 = 65,253 Pa = 489.3 mmHg 1/T₂ = 1/373.15 − (8.314/40700) × ln(65253/101325) = 0.002680 − 0.0002043 × (−0.4401) = 0.002680 + 0.0000899 = 0.002770 T₂ = 1/0.002770 = 361.0 K = 87.9°C ≈ 88°CAt Leh's altitude, water boils at approximately 88°C — 12°C below sea-level. Dal and rajma require 40–50% longer cooking time than at sea level; a pressure cooker rated at 1 bar gauge (2 bar absolute at sea level) will produce about 115°C inside at Leh altitude, restoring adequate cooking temperatures.
Frequently Asked Questions
At high altitude, atmospheric pressure is lower than at sea level. Boiling occurs when a liquid's vapour pressure equals the surrounding atmospheric pressure. At lower atmospheric pressure, water's vapour pressure equals it at a lower temperature — so water boils at less than 100°C. For every 300 m of altitude gain, the boiling point of water drops by approximately 1°C. At 3,500 m (Leh, Ladakh), water boils at about 87°C; at 5,364 m (Everest Base Camp), at about 82°C.
Sea level (Mumbai, Chennai, Kochi): 100°C. Bengaluru (920 m): 97°C. Pune (560 m): 98°C. Ooty (2,240 m): 92°C. Shimla (2,205 m): 92°C. Manali (2,050 m): 93°C. Darjeeling (2,050 m): 93°C. Leh (3,500 m): 87°C. Siachen Base Camp (3,600 m): 87°C. Everest Base Camp (5,364 m): 82°C. Summit of Everest (8,849 m): 70°C — too low to brew tea (minimum 85°C needed for acceptable cup).
At a lower boiling point, water is less hot, so cooking by boiling takes longer. Foods that require sustained exposure to high temperatures are most affected. Dal and rajma that take 20–25 minutes at sea level may take 35–40 minutes at 2,500 m altitude. Rice may remain undercooked. Eggs require longer boiling. The standard solution is a pressure cooker, which raises internal pressure above 1 atm and therefore raises the boiling point back above 100°C inside the vessel — restoring normal cooking temperatures.
The barometric formula gives atmospheric pressure as a function of altitude: P = P₀ × (1 − 2.2557×10⁻⁵ × h)^5.25588, where P₀ = 101,325 Pa (sea level), h is altitude in metres, and the exponent 5.25588 accounts for the temperature lapse rate in the standard atmosphere. This gives P in Pascals; divide by 133.322 for mmHg. At 2,000 m: P = 101325 × (1 − 0.04511)^5.256 = 101325 × 0.784 = 79,495 Pa = 596 mmHg.
Enter the altitude in metres in the Altitude field (range 0 to 8,849 m, the height of Everest). The calculator computes atmospheric pressure using the barometric formula, then uses the Clausius-Clapeyron equation with water's ΔHvap = 40.7 kJ/mol to find the boiling point at that pressure. Results are shown in °C, °F, mmHg, and kPa.
At the summit of Mount Everest (8,849 m), atmospheric pressure is approximately 253 mmHg (about 33% of sea level pressure). The boiling point of water at this pressure, calculated using the Clausius-Clapeyron equation, is approximately 70°C. This temperature is too low to brew proper tea, cook food safely, or sterilise equipment by boiling. Expedition teams at high altitude rely on pressure cookers for cooking and pre-packaged sterile medical supplies rather than boil-sterilisation.
This calculator is specifically calibrated for water using ΔHvap = 40.7 kJ/mol and T_ref = 100°C at 760 mmHg. For other liquids (ethanol, acetone, etc.), use the [Boiling Point Calculator](/boiling-point-calculator/) where you can input the substance's specific ΔHvap and normal boiling point, then enter the calculated altitude pressure in mmHg as the target pressure.
A pressure cooker seals the cooking vessel and allows steam pressure to build up inside. At typical pressure cooker gauge pressures of 0.7–1.0 bar above ambient, the internal absolute pressure is 1.7–2.0 atm (1292–1520 mmHg). At this elevated internal pressure, water boils at 115–121°C regardless of external altitude. This is why pressure cookers are essential equipment in high-altitude kitchens — they restore near-sea-level cooking temperatures even at altitudes like Leh or Shimla.
Yes — pharmaceutical manufacturers operating at high-altitude sites must account for this in sterilisation processes. The autoclave sterilisation standard requires 121°C at 1 atm gauge (2 atm absolute, 1520 mmHg) for 15–20 minutes. At an altitude of 2,000 m, the atmospheric pressure is only 596 mmHg — so the absolute pressure inside the autoclave must be 596 + 760 = 1356 mmHg to achieve 121°C, rather than the 1520 mmHg required at sea level. Autoclave manufacturers specify pressure settings in absolute terms to account for local altitude.
The barometric lapse rate describes how quickly atmospheric pressure decreases with altitude. In the standard atmosphere (International Standard Atmosphere), pressure drops approximately 12 Pa per metre near sea level, but less rapidly at higher altitudes (the relationship is exponential, not linear). Temperature also decreases with altitude (the thermal lapse rate is about −6.5°C/km in the standard atmosphere), which means ΔHvap of water changes slightly with altitude. The Clausius-Clapeyron calculation in this tool assumes constant ΔHvap = 40.7 kJ/mol, which is a reasonable approximation over the temperature range encountered.