Altitude Sickness Risk Calculator
A structured way to apply the Wilderness Medical Society consensus guidelines: how fast you gain sleeping altitude, how acclimatized you are, and your history.
Result
- WMS guideline: above 3,000 m, raise your sleeping altitude by no more than 500 m per day, with a rest day every 1,000 m.
- Add an acclimatization night: sleeping at the current altitude before moving up is the single strongest risk reducer.
Keep exertion easy on the first day at each new sleeping altitude and drink enough to keep urine pale.
How the calculation works
The calculator scores four inputs the way wilderness-medicine consensus weights them: per-day sleeping-altitude gain (against the 500 m guideline above 3,000 m), nights already spent acclimatizing above 2,500 m, the starting altitude, and any personal history of AMS or HAPE/HACE. The total maps to low, moderate or high risk with matching suggestions:
Educational estimate only - not medical advice. Severe headache, vomiting, confusion, breathlessness at rest or a wet cough mean descend immediately and seek medical care.
The full prevention picture - itineraries, red flags and what descent actually treats - is in the altitude sickness prevention guide. The environmental side of altitude - cold nights and slow cooking - is on the altitude temperature and boiling point calculators.
Planning estimate only - not safety advice.
Frequently asked questions
What is the 500-meter rule?
The Wilderness Medical Society consensus: above 3,000 m, raise your sleeping altitude by no more than 500 m per day, and include a rest day for every 1,000 m gained. It is the single most evidence-backed altitude guideline there is, and the calculator scores your itinerary against it directly.
What is the difference between AMS, HAPE and HACE?
AMS is the common, usually mild form: headache plus nausea, fatigue or poor sleep above altitude. HACE (brain) and HAPE (lungs) are rare, life-threatening progressions with distinct red flags - confusion or inability to walk a straight line; breathlessness at rest or a wet cough. Both demand immediate descent.
Does previous altitude sickness mean I will get it again?
It is the strongest individual risk factor - a prior AMS roughly doubles the odds, and a history of HAPE or HACE raises them more. It does not doom you: slower ascent profiles and preventive medication discussed with a doctor work. The calculator weights history accordingly.
Who is this calculator for?
Healthy adults planning treks and climbs who want a structured read on their itinerary - how aggressive the ascent profile is relative to consensus advice. It is not a medical screening tool and knows nothing about your health, medications or the specific route. When in doubt, build an acclimatization day.
Does hydration or fitness protect against AMS?
Fitness does not - elite athletes acclimatize at the same speed and push harder into symptoms. Hydration helps you feel better but does not prevent AMS. Time at altitude is the only reliable natural acclimatizer, which is why the whole model keys on sleeping altitude.