Altitude Sickness Risk Calculator
Estimate your risk of Acute Mountain Sickness (AMS) based on your current altitude, target altitude, and ascent rate.
Plan safe acclimatization.
Acute Mountain Sickness (AMS) occurs when the body does not acclimatize fast enough to reduced oxygen levels at altitude. It affects 25% of people who ascend to 2,500 m (8,200 ft) and 50-85% of those who ascend rapidly to 4,500 m (14,750 ft).
Safe ascent rate guidelines (above 2,500 m):
- Ascend no more than 300-500 m per day in sleeping altitude
- “Climb high, sleep low” — daytime excursions above camp altitude are fine
- For every 1,000 m gained in sleeping altitude, take one rest day
AMS symptoms: Headache (required for diagnosis) plus one of: nausea, fatigue, dizziness, difficulty sleeping. Onset typically 6-12 hours after arrival at new altitude.
Risk factors that increase AMS chance:
- Previous history of AMS (strongest predictor)
- Fast ascent rate (biggest controllable factor)
- High sleeping altitude
- Physical exertion (especially on first day)
- Age under 50 is slightly higher risk than older adults (counterintuitive)
- Alcohol in first 24 hours at altitude worsens acclimatization
When to descend immediately: High Altitude Cerebral Edema (HACE) — confusion, ataxia, loss of consciousness. High Altitude Pulmonary Edema (HAPE) — breathlessness at rest, crackling breath sounds, pink frothy sputum. Both are life-threatening.
Prevention: Slow ascent, acetazolamide (Diamox) prophylaxis for high-risk individuals (prescription required), stay hydrated, avoid alcohol, light activity on first day.