About the Formula

At sea level, the atmospheric pressure is about 101.3 kilopascals, and water boils at 100 °C. As you travel to higher elevations, air pressure decreases, and water boils at a lower temperature. This calculator uses the barometric formula to estimate ambient pressure based on altitude and then applies the Clausius-Clapeyron relation to find the corresponding boiling point. The pressure model assumes standard atmospheric conditions, so results are close to reality for most temperate climates but can vary with weather. Still, it’s a useful approximation when planning recipes or equipment settings in the mountains.

The barometric formula used here is P = 101.325 × (1 - 2.25577 × 10^-5 × h)^5.2559, where h is the elevation in meters and P is the pressure in kilopascals. This equation is derived from the International Standard Atmosphere model and represents how air pressure declines with height in the troposphere. By plugging in your elevation, we can estimate the local pressure without needing a specialized barometer.

Once we have the estimated pressure, we compute the boiling point using the relation T = 49.161 × ln(P) + 44.932, where T is the boiling temperature in degrees Celsius and ln is the natural logarithm. This expression comes from rearranging the Clausius-Clapeyron equation for water and provides good accuracy across typical elevations encountered on Earth. At 101.3 kPa, the result is effectively 100 °C. As pressure drops, so does the boiling point, which is why foods take longer to cook at high altitudes.

Understanding how boiling point changes with elevation is important for both cooking and safety. In the kitchen, water that boils at 95 °C will not cook pasta or rice as quickly as water at 100 °C. You may need to extend boiling time or adjust recipes. When pressure canning or sterilizing medical equipment, a lower boiling temperature means you must maintain pressure longer to kill bacteria effectively. Mountaineers and hikers also rely on these principles when melting snow or purifying water in the backcountry, since boiling alone may not be sufficient at very high altitudes.

One interesting side effect is that beverages like tea or coffee can taste slightly different when brewed at elevation. Because the water temperature never reaches a full 100 °C, extraction occurs more slowly, and the final flavor profile changes. Professional baristas who serve customers in mountainous regions often tweak their brewing parameters to achieve the desired taste. This calculator helps them anticipate the exact temperature they’ll be working with on a given day.

For engineers, altitude-related boiling point calculations inform the design of cooling systems, pressure vessels, and industrial processes. Chemical reactions that require precise temperatures might behave unpredictably if performed at a significantly different elevation than planned. Pressure cookers rely on sealed environments to raise the boiling point, which in turn cooks food faster. Understanding how altitude interacts with these systems can prevent undercooked meals or inefficient thermal management.

The human body also responds to reduced pressure at altitude. Lower boiling temperatures coincide with thinner air, which can lead to altitude sickness as less oxygen is available. While this calculator focuses on the temperature of boiling water, keep in mind that the surrounding environment changes in other ways as you climb higher. Hydration becomes more important, and the risk of dehydration increases because water vapor evaporates faster in dry mountain air.

You can experiment with this tool by entering altitudes from sea level to the height of famous mountains. Try 8848 meters, the height of Mount Everest, and observe how the boiling point plummets to around 70 °C. At such low temperatures, cooking and sterilization become significant challenges. By contrast, at a modest 1,500 meters— roughly the elevation of Denver, Colorado— water boils at about 95 °C. Recipes often recommend increasing boiling time by several minutes in these conditions, and bakers adjust leavening agents to compensate for the thinner air.

Because this calculator runs entirely in your browser, it’s ideal for quick estimates on the go. Whether you’re planning a camping trip, adjusting your home canning routine, or curious about the physics of boiling, simply enter an altitude and get an instant result. Bookmark it on your phone or laptop so you have access even when you’re offline in remote areas.

From mountaineers brewing tea at base camp to scientists running experiments in alpine research stations, boiling point calculations serve a surprising range of purposes. Use this tool to deepen your understanding of how pressure, temperature, and altitude interact. The next time you’re above sea level and watching a pot on the stove, you’ll know exactly why those bubbles form at a slightly different temperature than you’re used to.