Altitude sickness risk calculator

Enter the highest planned sleeping altitude, the altitude where the ascent begins, the number of ascent days, and whether you have experienced AMS before. The calculator reports the net gain, average daily ascent, a risk category, and whether a slower acclimatization schedule is advisable. It cannot predict exactly who will become ill, and it does not replace advice from a clinician familiar with high-altitude travel.

Use sleeping altitude to describe the itinerary

Altitude illness risk depends strongly on where you sleep, how quickly you reach that elevation, and your own previous response to altitude. Enter the highest place where you plan to sleep as the destination, rather than the highest pass, viewpoint, or summit visited briefly during the day. For the starting altitude, use the elevation where you normally sleep before the ascent or the last established sleeping stop on a staged itinerary. The ascent-days value is the time over which that sleeping-altitude gain occurs. For example, flying from sea level and sleeping at a mountain resort that evening is approximately a one-day ascent, even if the flight itself takes only a few hours. A trek with overnight stops should use the number of days from its initial sleeping elevation to the highest planned sleeping elevation. The calculator converts those entries into an average gain per day. That average cannot show every sharp jump in a complex itinerary, so assess individual overnight legs too. A single large increase may matter even when the trip-wide average appears comfortable.

Understand the estimate and its limits

The result combines destination altitude, average ascent rate, rapid arrival from below 2,500 meters, and a reported history of acute mountain sickness. Higher destinations and faster gains add concern, while a previous episode moves the estimate upward because past response is useful personal evidence. The categories are screening labels, not probabilities or diagnoses. People on the same itinerary can respond very differently, and excellent physical fitness does not protect someone from AMS. The algorithm deliberately avoids pretending that age, training, or athletic performance can make a rapid ascent safe. It also does not evaluate pregnancy, heart or lung disease, medications, sleep disorders, alcohol use, or a detailed history of severe altitude illness. Anyone with significant medical conditions, a previous severe reaction, or plans for remote high-altitude travel should review the itinerary with a qualified clinician. The displayed minimum ascent days is a simple planning reference based on limiting average sleeping-altitude gain to about 500 meters per day; it is not a guarantee and may need additional rest days.

Act on symptoms instead of relying on the score

Use the estimate while planning, then let symptoms govern decisions on the mountain. Typical acute mountain sickness involves a headache after gaining altitude together with symptoms such as nausea, dizziness, unusual fatigue, or disturbed sleep. Do not continue upward when these symptoms appear. Rest at the same elevation, tell companions, and be prepared to descend if symptoms do not improve or become worse. Confusion, inability to walk normally, severe weakness, or breathlessness at rest can signal life-threatening high-altitude cerebral or pulmonary edema and require immediate descent and urgent medical care. Do not wait for the calculator, a scheduled rest day, or morning to reconsider the plan. Gradual ascent reduces risk but never eliminates it, so preserve flexibility in bookings and turnaround decisions. Avoid treating this score as permission to push through illness. For organized trips, share sleeping elevations and contingency routes with the group. For independent travel, identify where descent, oxygen, communications, and medical help are available before leaving. Prevention planning works best when the itinerary includes time to respond rather than merely meeting a numerical target.