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Altitude Sickness Risk Calculator

Estimate acute mountain sickness risk based on ascent rate and Lake Louise Score.

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For educational reference only. Not a medical diagnosis. If you have HACE or HAPE symptoms (ataxia, confusion, breathlessness at rest), descend immediately and seek emergency help.

Your altitude at start of the day (trailhead or previous camp)

Altitude where you plan to sleep tonight

Auto-calculated from start → target altitude

Nights already spent above 2500m on this trip

Sleeping 3500m · +2000m ascent · 0 prior nights · 0 risk factors → 85% estimated risk

ESTIMATED AMS RISK

85%

Extreme

Extreme risk. Do not ascend further without acclimatization. Consider descent.

Sleeping altitude: 3500m (11,483 ft)

Also useful: Naismith's Rule Calculator → · Turnaround Time Calculator →

Based on Lake Louise AMS Consensus · Wilderness Medical Society guidelines

Altitude sickness explained

How to prevent altitude sickness

Ascent rate — the most important factor

  • Above 3000m: gain a maximum of 300–500m of sleeping altitude per day
  • For every 1000m gained above 3000m, spend one extra rest/acclimatization day
  • Arriving by plane or fast transport to high altitude is a major risk — allow time to acclimatize

Climb high, sleep low

Day-hike to higher altitude, then return to a lower camp to sleep. Your body adapts to the high altitude stimulus while sleeping at a safer elevation. This is the gold standard technique for expeditions.

Hydration and medication

  • Stay well hydrated — dehydration worsens symptoms
  • Avoid alcohol and sedatives in the first 48h at each new altitude
  • Acetazolamide (Diamox) 125–250mg twice daily is proven prophylaxis — consult a doctor before your trip
  • Ibuprofen 400–600mg can treat AMS headache but does not cure AMS

Fitness level does not protect against AMS — well-trained athletes are just as susceptible. Prior episodes of AMS are the strongest predictor of future episodes.

Frequently asked questions

What altitude causes altitude sickness?

AMS typically begins above 2500m (8200 ft). Risk increases significantly above 3000m and becomes very high above 4000m. The key factor is not just altitude but ascent rate — gaining more than 500m of sleeping altitude per day above 3000m dramatically increases risk.

What is the Lake Louise Score?

The Lake Louise Score is the clinical standard for diagnosing AMS. It scores five symptoms (headache, nausea, fatigue, dizziness, sleep disturbance) from 0-3 each. A score of 3 or more with headache present confirms AMS. A score of 6 or more indicates moderate to severe AMS requiring immediate descent.

How fast is safe to ascend?

Above 3000m, gain no more than 300-500m of sleeping altitude per day. Every 1000m gained above 3000m, spend a rest day acclimatizing. The "climb high, sleep low" technique — hiking to higher altitude during the day but returning to sleep lower — is very effective for acclimatization.

When should I descend for altitude sickness?

Descend immediately if you experience HACE symptoms (stumbling walk, confusion, altered consciousness) or HAPE symptoms (breathlessness at rest, pink frothy sputum, cyanosis). For mild AMS (Lake Louise Score 3-5), do not ascend and rest. For moderate AMS (score 6+), descend 300-1000m immediately.

Does fitness protect against altitude sickness?

No — fitness level does not protect against AMS. Well-trained athletes are just as susceptible as unfit individuals. The body's acclimatization response is determined by physiology, not fitness. The best predictor of AMS susceptibility is prior personal history of AMS at altitude.

Does Diamox (acetazolamide) prevent altitude sickness?

Acetazolamide (Diamox) is proven to significantly reduce AMS risk when started 24h before ascent and continued for 2 days at target altitude. The typical prophylactic dose is 125-250mg twice daily. It is available on prescription in most countries. Common side effects include increased urination and tingling in hands and feet. Consult a doctor before use.