Boiling Point at Altitude Calculator
Calculate the boiling point of water at any altitude or elevation. As you go higher, atmospheric pressure drops, and water boils at a lower temperature. Enter your altitude to find the exact boiling point.
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What Is the Boiling Point?
The boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure surrounding the liquid. At this temperature, the liquid transitions into a gas (steam, in the case of water). At standard sea-level pressure (1 atm or 101.325 kPa), pure water boils at exactly 100°C (212°F or 373.15 K).
Boiling is different from evaporation, which occurs at any temperature on the surface of a liquid. Boiling happens throughout the entire volume of the liquid when the vapor pressure is sufficient to overcome the surrounding atmospheric pressure. This is why you see bubbles forming from the bottom of a pot when water reaches its boiling point.
Why Does Boiling Point Change with Altitude?
As altitude increases, the column of air above you becomes shorter and less dense. This means there is less atmospheric pressure pushing down on the surface of the water. Since boiling occurs when a liquid's vapor pressure matches the surrounding pressure, lower atmospheric pressure means the water doesn't need to be heated as much to boil.
In simple terms: less air pressure above the water means it's easier for water molecules to escape into the gas phase, so boiling happens at a lower temperature. For roughly every 150 meters (500 feet) of elevation gain, the boiling point of water drops by approximately 0.5°C (about 1°F).
This is why cooking at high altitudes takes longer — the water boils at a lower temperature, so food cooks more slowly even though the water is boiling vigorously.
The Relationship Between Atmospheric Pressure and Altitude
Atmospheric pressure decreases approximately exponentially with altitude. At sea level, the standard atmospheric pressure is 101,325 Pa (1 atm). As you ascend, the pressure drops because there is less air above you exerting its weight.
Key pressure values at various altitudes:
- Sea level (0 m): 101,325 Pa (1.000 atm)
- Denver, CO (1,609 m): ~83,400 Pa (0.823 atm)
- La Paz, Bolivia (3,640 m): ~64,300 Pa (0.635 atm)
- Mount Everest summit (8,849 m): ~31,400 Pa (0.310 atm)
The Barometric Formula Explained
The barometric formula is a mathematical model that describes how atmospheric pressure decreases with increasing altitude in the Earth's atmosphere. For altitudes within the troposphere (up to about 11,000 m), we use:
Where each variable represents:
- P = pressure at altitude h (Pascals)
- P₀ = 101,325 Pa — standard sea-level atmospheric pressure
- L = 0.0065 K/m — temperature lapse rate (how fast temperature drops with altitude)
- h = altitude above sea level (meters)
- T₀ = 288.15 K (15°C) — standard sea-level temperature
- g = 9.80665 m/s² — gravitational acceleration
- M = 0.0289644 kg/mol — molar mass of dry air
- R = 8.31447 J/(mol·K) — universal gas constant
The exponent g×M/(R×L) evaluates to approximately 5.2559, which is a dimensionless constant. This formula assumes a linear decrease in temperature with altitude, which is a good approximation in the troposphere.
The Clausius-Clapeyron Equation
Once we know the atmospheric pressure at a given altitude, we use the Clausius-Clapeyron equation to determine the boiling point at that pressure. The equation relates the boiling point of a liquid to pressure changes:
Where:
- T₁ = 373.15 K (100°C) — boiling point at standard pressure
- T₂ = boiling point at the new pressure (what we want to find)
- P₁ = 101,325 Pa — standard atmospheric pressure
- P₂ = atmospheric pressure at the given altitude
- R = 8.31447 J/(mol·K) — universal gas constant
- ΔHvap = 40,660 J/mol — enthalpy of vaporization of water
How to Calculate Boiling Point at Any Altitude — Step by Step
Determine Your Altitude
Find the elevation of your location in meters. You can use a GPS device, a mapping app, or look it up online. Convert to meters if needed (1 foot = 0.3048 m, 1 km = 1000 m, 1 mile = 1609.34 m).
Calculate Atmospheric Pressure
Apply the barometric formula: P = 101325 × (1 - 0.0065 × h / 288.15)^5.2559. For example, at 2000 m: P = 101325 × (1 - 0.0065 × 2000 / 288.15)^5.2559 = 101325 × 0.9549^5.2559 ≈ 79,498 Pa.
Apply the Clausius-Clapeyron Equation
Use the Clausius-Clapeyron equation: 1/T₂ = 1/T₁ + (R/ΔHvap) × ln(P₁/P₂). For our example at 2,000 m where P = 79,498 Pa:
1/T₂ = 1/373.15 + (8.31447/40660) × ln(101325/79498) = 0.002680 + 0.0002045 × 0.2424 = 0.002680 + 0.0000496 = 0.002730. Therefore T₂ = 1/0.002730 = 366.3 K = 93.2°C. The boiling point has decreased by about 6.8°C compared to sea level.
Convert to Your Desired Unit
Convert from Kelvin to Celsius (°C = K - 273.15), Fahrenheit (°F = K × 9/5 - 459.67), or keep in Kelvin.
Table of Boiling Points at Common Altitudes
The following table shows the boiling point of water at various common altitudes, calculated using the barometric formula and Clausius-Clapeyron equation:
| Location / Altitude | Altitude (m) | Pressure (atm) | Boiling Point (°C) | Boiling Point (°F) |
|---|---|---|---|---|
| Sea Level | 0 | 1.000 | 100.0 | 212.0 |
| Low Hills | 500 | 0.942 | 98.3 | 208.9 |
| Mountain Town | 1,000 | 0.887 | 96.7 | 206.0 |
| Highland City | 1,500 | 0.834 | 95.0 | 203.0 |
| High Plateau | 2,000 | 0.785 | 93.3 | 199.9 |
| High Mountain | 3,000 | 0.692 | 90.0 | 194.0 |
| Very High Altitude | 5,000 | 0.533 | 83.3 | 181.9 |
| Mt. Everest Summit | 8,849 | 0.310 | 69.9 | 157.8 |
Practical Implications for Cooking at High Altitudes
The lower boiling point of water at high altitudes has significant practical consequences, especially for cooking. Here are the key effects:
- Longer cooking times: Since water boils at a lower temperature, food takes longer to cook. Boiled pasta, rice, vegetables, and eggs all require extended cooking times at high elevation.
- Baking challenges: Leavening gases expand more quickly at lower pressure, causing baked goods to rise too fast and then collapse. You may need to reduce baking powder/soda, increase oven temperature, and adjust liquid amounts.
- Faster evaporation: Water evaporates more quickly at high altitudes, which can dry out foods. You may need to add more liquid to recipes, cover pots more often, and use lower heat settings.
- Candy making: Sugar solutions and candy reach their "soft ball" or "hard crack" stages at lower temperatures. Most candy thermometer charts need adjustment at altitude.
- Pressure cookers become essential: A pressure cooker raises the boiling point back toward 100°C by increasing pressure inside the sealed pot, making it invaluable for high-altitude cooking.
- Beans and legumes: Dried beans can be very difficult to cook properly at high altitude without a pressure cooker, as the lower boiling point may not be sufficient to break down certain proteins.
Tips for Cooking at High Altitude
Boiling & Simmering
- Increase cooking time by 25% for every 1,000 m (3,300 ft) above sea level.
- Use a lid on pots to retain heat and moisture.
- Consider using a pressure cooker for beans, grains, and tough cuts of meat.
- Add 1–2 minutes per egg when hard-boiling at altitudes above 1,500 m.
Baking Adjustments
- Reduce baking powder by 15–25% for every 1,000 m above sea level.
- Increase oven temperature by 10–15°C (15–25°F).
- Add 2–4 tablespoons of extra flour per cup to strengthen the structure.
- Reduce sugar by 1–3 tablespoons per cup to prevent over-browning.
- Increase liquid by 2–4 tablespoons per cup to compensate for faster evaporation.
General High-Altitude Tips
- Store flour and sugar in airtight containers, as dry air at altitude draws moisture out faster.
- Water boils faster but at a lower temperature — vigorous boiling does NOT mean hotter water.
- Deep-frying temperatures should be reduced by about 2–3°C per 1,000 m elevation.
- Yeast doughs rise faster at high altitude; reduce rise time or use less yeast.
Frequently Asked Questions
At what temperature does water boil on Mount Everest?
At the summit of Mount Everest (8,849 m / 29,032 ft), atmospheric pressure is only about 0.31 atm (31.4 kPa). At this pressure, water boils at approximately 69.9°C (157.8°F). This temperature is too low to cook many foods properly, which is why climbers rely on pressure cookers or pre-cooked meals.
Does altitude affect the boiling point of liquids other than water?
Yes! Altitude (and therefore atmospheric pressure) affects the boiling point of all liquids, not just water. Any liquid's boiling point is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. So milk, broth, alcohol, and other liquids will all boil at lower temperatures at higher altitudes. The exact change depends on each liquid's enthalpy of vaporization.
Why does a pressure cooker work at high altitude?
A pressure cooker is a sealed vessel that traps steam, building up internal pressure well above atmospheric pressure. This higher pressure raises the boiling point of water inside the cooker — typically to about 121°C (250°F) at 1 atm of gauge pressure. At high altitude, where the ambient boiling point may be as low as 90°C, a pressure cooker restores and even exceeds the normal 100°C boiling point, allowing food to cook properly and quickly.
Can water boil at room temperature?
Yes, if the pressure is low enough! In a vacuum chamber, water can boil at room temperature (around 20–25°C). This happens because the vapor pressure of water at room temperature (about 2.3 kPa) is sufficient to cause boiling when the surrounding pressure is reduced to that level. This principle is used in various industrial processes, including freeze-drying food.
How accurate is this calculator?
This calculator uses the International Standard Atmosphere barometric formula and the Clausius-Clapeyron equation, both of which are well-established scientific models. The results are accurate to within about ±0.5°C for altitudes up to about 9,000 m. Real-world conditions (weather, humidity, local temperature) can cause slight variations from the calculated values. The calculator assumes standard atmospheric conditions and pure water.
Does adding salt to water change the boiling point at altitude?
Adding salt (or any solute) to water raises its boiling point — this is called boiling point elevation. However, the effect is very small for typical cooking amounts. Adding one tablespoon of salt to a liter of water raises the boiling point by only about 0.5°C. This minimal increase does not significantly offset the reduction caused by altitude. You would need an impractically large amount of salt to make a meaningful difference.
Is there an altitude where water cannot boil because it freezes first?
At extremely high altitudes (or very low pressures), both the boiling point and the freezing point approach each other. At the "triple point" of water (611.73 Pa pressure, 0.01°C), water can exist as solid, liquid, and gas simultaneously. Below this pressure, liquid water cannot exist — ice sublimates directly into vapor. However, you would need to be well above the stratosphere (around 18–20 km altitude in standard conditions) to reach this pressure naturally.