About the Boiling Point Calculator
The Boiling Point Calculator returns the temperature at which water boils for any altitude or barometric pressure, applying the Clausius–Clapeyron equation with water’s enthalpy of vaporization (40.66 kJ/mol). City presets cover the common high-altitude cooking destinations (Denver, Mexico City, Quito, La Paz, Bogotá), or you can enter a custom altitude in feet or meters and override the standard pressure if your barometer says otherwise.
It is built for high-altitude home cooks who keep producing dense bread and gummy pasta, mountaineers planning a freeze-dried meal at elevation, science teachers demonstrating pressure-temperature relationships, brewers and distillers calibrating column temperatures, and anyone moving from sea level to Denver and quietly wondering why their pressure cooker behaves differently.
All calculation happens in JavaScript on your device. Altitude, pressure, and city-preset selections never leave your browser. The page makes no network call after first load. City altitude data is bundled as static JSON, so even your destination choice is private.
The Clausius–Clapeyron approximation assumes ideal-gas behavior and a constant enthalpy of vaporization, which is excellent for water between sea level and roughly 15,000 feet. Above that, pressure drops nonlinearly and the approximation accumulates error. The cooking adjustments (longer simmer times, slight oven-temperature increases, reduced sugar in baking) are rules of thumb refined by the King Arthur Baking Company and the Colorado State University Extension; treat them as starting points and trust your eye over the rule.
| Altitude | °F | °C | Pressure (kPa) |
|---|
Boiling point inside a pressure cooker at your current altitude, plus adjusted cook times.
Why Water Boils at Different Temperatures at Different Altitudes
Water boils when its vapor pressure equals the atmospheric pressure pushing down on its surface. At sea level, standard atmospheric pressure is 101.325 kPa (14.696 psi, or 1 atm), and water reaches that equilibrium at 100°C (212°F). As you climb in elevation, the column of air above you becomes shorter and less dense, which means less atmospheric pressure is pressing down on the water’s surface. With less pressure to overcome, water molecules escape into vapor at a lower temperature. For roughly every 500 feet (150 m) of elevation gain, the boiling point drops by about 0.9°F (0.5°C). At Denver’s altitude of 5,280 feet, that works out to approximately a 9°F drop — water boils at 203°F instead of 212°F. At the summit of Mount Everest (29,032 feet), the boiling point plummets to about 160°F (71°C), too low to properly cook many foods.
The Clausius–Clapeyron Equation (Simplified)
The relationship between pressure and boiling point is governed by the Clausius–Clapeyron equation. In its simplified integrated form it reads: ln(P₂/P₁) = (ΔHvap/R) × (1/T₁ − 1/T₂), where P₁ and T₁ are the reference pressure and temperature (101.325 kPa and 373.15 K at sea level), P₂ is the local atmospheric pressure, ΔHvap is the molar heat of vaporization of water (approximately 40,660 J/mol near 100°C), and R is the universal gas constant (8.314 J/(mol·K)). Solving for T₂ gives the boiling point at any pressure. This calculator first converts altitude to pressure using the barometric formula P = P₀ × (1 − 0.0000225577 × h)5.25588, where h is altitude in meters, then feeds that pressure into the Clausius–Clapeyron equation to obtain the boiling point. The result is accurate to within about 0.1°C for typical terrestrial conditions.
High-Altitude Cooking Adjustments: Complete Guide
When water boils at a lower temperature, foods cooked in boiling water take longer to reach the internal temperatures needed for safety and proper texture. Pasta that takes 10 minutes at sea level may need 12–14 minutes at 7,000 feet. Hard-boiled eggs that finish in 12 minutes at the coast may require 15–18 minutes in the mountains. Beans, stews, and soups that simmer for hours in a stockpot become particularly affected because the entire cooking temperature is depressed — a slow-cooked stew at 7,000 feet reaches only about 199°F (93°C) instead of 212°F. Pressure cookers are the most effective workaround because they raise the boiling point back above 212°F by increasing the pressure inside the sealed vessel. At 15 PSI above atmospheric, even at 10,000 feet, the boiling point inside the cooker exceeds 250°F (121°C), which actually cooks food faster than sea-level boiling.
High-Altitude Baking: Temperature, Time, and Ingredient Changes
Baking at altitude is more complex than boiling because it involves gas expansion, protein coagulation, and moisture evaporation simultaneously. At high altitude, leavening gases (from baking soda, baking powder, and yeast) expand more readily because there is less atmospheric pressure holding them in check. This causes batters and doughs to rise faster and higher, often before the protein structure has set, which leads to collapsed cakes and dense, gummy centers. The general rules are to increase oven temperature by 15–25°F so the outside structure sets faster, reduce sugar by 1–3 tablespoons per cup (sugar weakens the protein structure and too much makes collapse more likely), reduce leavening by 15–25% (less gas means less over-rising), and add 2–4 tablespoons of extra liquid per cup of flour to compensate for the faster moisture evaporation in dry mountain air. Cooking times may increase by 5–15% despite the higher oven temperature because the lower boiling point means internal moisture takes longer to reach the temperature needed to set starches and proteins.
Boiling Points on Other Planets
Atmospheric pressure varies dramatically across the solar system, producing exotic boiling point conditions. On Mars, the average surface pressure is about 0.6 kPa — less than 1% of Earth’s — which means liquid water would boil at roughly 2°C (35°F) if it existed on the surface. On Venus, the crushing atmospheric pressure of 9,200 kPa (about 91 times Earth’s) would push the boiling point of water above 300°C (572°F). On Titan, Saturn’s largest moon, the atmospheric pressure is about 147 kPa (1.45 atm), but the surface temperature is −179°C (−290°F), so the relevant boiling liquid is methane, not water. Jupiter’s atmosphere has no solid surface, but at the altitude where pressure equals 1 atm, water would behave much as it does at sea level on Earth — boiling at 100°C. These comparisons illustrate that boiling point depends entirely on pressure, not on any intrinsic property of the planet itself.
Looking for more science and math tools? Browse all Math & Science tools for graphing calculators, statistics, and unit conversions.
Frequently Asked Questions
At what temperature does water boil?
At standard atmospheric pressure (101.325 kPa or 1 atm, sea level) water boils at 100 degrees C (212 degrees F). The boiling point drops as atmospheric pressure decreases with elevation.
How much does the boiling point drop per 1,000 feet of elevation?
Roughly 1.8 degrees F (1.0 degrees C) per 1,000 feet. More precisely, the boiling point falls about 0.9 degrees F (0.5 degrees C) per 500 feet gained above sea level.
At what temperature does water boil in Denver?
Denver sits at 5,280 feet, where atmospheric pressure drops to about 83 kPa. Water there boils at approximately 203 degrees F (95 degrees C), about 9 degrees F lower than sea level.
Why does food take longer to cook at high altitude?
Because water boils at a lower temperature, the heat transferred to food is lower. Pasta, eggs, beans, and stews simmer in cooler water, so their proteins and starches take noticeably longer to break down.
What formula relates boiling point to pressure?
The Clausius-Clapeyron equation links vapor pressure to temperature: ln(P2/P1) = -(dHvap/R)(1/T2 - 1/T1), where dHvap is the enthalpy of vaporization (40.66 kJ/mol for water) and R is the gas constant (8.314 J/mol-K).