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Boiling Point at Altitude Calculator

Chemistry

Calculate water's boiling point at any altitude from sea level to 8,849 m (Everest), using barometric pressure and the Clausius-Clapeyron equation.

Reviewed by the thecalcu.com team · Last updated February 12, 2026

08,849

Boiling Point (°C)

93.22
Boiling Point (°F)
199.8
Atmospheric Pressure (mmHg)
596.3
Atmospheric Pressure (kPa)
79.5

This calculator computes your Boiling Point (°C), Boiling Point (°F), Atmospheric Pressure (mmHg), Atmospheric Pressure (kPa) from the values you enter.

Inputs
Altitude (m)
Outputs
Boiling Point (°C)Boiling Point (°F)Atmospheric Pressure (mmHg)Atmospheric Pressure (kPa)

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.

Why Use a Boiling Point at Altitude Calculator?

The compound calculation, barometric formula → pressure → Clausius-Clapeyron boiling point, involves multiple steps and physical constants (standard sea-level pressure 101,325 Pa, lapse rate exponent 5.256, ΔHvap = 40,700 J/mol, R = 8.314 J/mol·K) that are difficult to look up and error-prone to chain together manually. This tool does it in one step.

For the 50+ million Indians living above 1,000 m altitude (Himachal Pradesh, Uttarakhand, J&K, Sikkim, high-altitude areas of Telangana, Karnataka, Maharashtra), knowing the local boiling point is practically useful for cooking, food safety, and pressure cooker selection.

Who Should Use This Calculator?

Home cooks and households at high altitude across Indian hill stations and mountainous states needing to adjust cooking times, confirm when to use a pressure cooker, and understand why food behaves differently at altitude compared to sea level.

Mountaineers and trekkers planning expeditions to the Himalayas who need to plan fuel, cooking equipment, and food safety procedures based on actual boiling temperatures at planned camp altitudes.

Food technologists and quality managers at high-altitude food processing facilities ensuring that thermal processes (blanching, pasteurisation, sterilisation) achieve required temperatures.

Pharmaceutical manufacturers and quality assurance teams at high-altitude manufacturing sites verifying that autoclave pressure settings achieve the required sterilisation temperature (121°C) despite reduced ambient pressure.

Physical chemistry students studying the practical applications of the Clausius-Clapeyron equation and barometric formula as real-world examples of phase equilibrium.

What Insights Does the Boiling Point at Altitude Calculator Give You?

Boiling Point (°C) is the primary output, the actual temperature at which water boils at the entered altitude. A value below 95°C indicates that cooking times should be significantly extended or a pressure cooker used. A value below 85°C (above approximately 5,000 m) means that tea brewing, egg boiling, and food safety by boiling water is compromised.

Boiling Point (°F) is the Fahrenheit equivalent for US-format engineering specifications, international expedition planning, and food safety guidelines expressed in Fahrenheit.

Atmospheric Pressure (mmHg) is the computed atmospheric pressure at the entered altitude, useful for setting up other pressure-dependent calculations, for specifying oxygen partial pressure during high-altitude physiology, and for autoclave pressure calculations.

Atmospheric Pressure (kPa) is the SI unit equivalent, standard for engineering and scientific applications.

How to use this BP at Altitude calculator

  1. 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.
  2. Read Boiling Point (°C), the temperature at which water boils at that altitude under open-air conditions.
  3. 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.
  4. 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.
  5. 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.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Step 1, Barometric formula:

P = P₀ × (1 − 2.2557 × 10⁻⁵ × h)^5.25588 P₀ = 101,325 Pa,  h = altitude in metres

Step 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°C

At 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

Why does water boil at a lower temperature at high altitude?
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.
What is the boiling point of water at various altitudes in India?
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).
How does lower boiling point affect cooking at high altitude?
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.
How is atmospheric pressure calculated at altitude?
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.
How do I use the Boiling Point at Altitude Calculator?
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.
What is the boiling point at the top of Mount Everest?
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.
Can this calculator be used for other liquids besides water?
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.
How does a pressure cooker overcome the altitude boiling point problem?
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.
Is the altitude effect on boiling point significant for pharmaceutical manufacturing?
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.
What is the barometric lapse rate and how does it affect boiling point?
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.