Altitude Acclimatization Planner
A night-by-night ascent profile that respects the 1,600 ft rule, plus how to recognise AMS, HACE and HAPE.
This is trip-planning arithmetic, not medical advice. Altitude illness can kill within hours, and no web page can assess anybody. If someone has symptoms that are getting worse, the answer is to go down — immediately, at night if necessary — and to get real medical help. Descent is the treatment.
A safe ascent profile
| Night | Sleep at | Gain | Oxygen |
|---|
Note that these are sleeping altitudes. You can go considerably higher during the day and come back down — that is what "climb high, sleep low" means, and it is genuinely helpful. What your body acclimatizes to is where you spend the night.
Check a plan you already have
The rules
Above about 8,000 feet, do not increase your sleeping altitude by more than roughly 1,600 feet a night, and take a rest day for every 3,300 feet gained. Below that height the rules do not really bite, which is why the first day of a trip can be a big jump.
Acclimatization is not fitness and cannot be trained beforehand. Fit young people get altitude sickness at least as often as anyone else, partly because they ascend faster. Susceptibility is largely individual and fairly consistent — if you have had trouble before, plan for it again.
- Any illness at altitude is altitude illness until proven otherwise.
- Never ascend with symptoms of AMS.
- If symptoms are getting worse, descend — immediately, and at night if necessary.
- Climb high, sleep low: your sleeping altitude is what your body acclimatizes to.
- Nobody with symptoms is left alone, and nobody descends alone.
Recognising it
- Headache, which is the defining symptom — no headache, no AMS
- Nausea or loss of appetite
- Unusual fatigue or weakness
- Dizziness or light-headedness
- Difficulty sleeping
What to do: Stop ascending. Do not sleep higher until the symptoms have gone. Most cases resolve in a day or two at the same altitude, and rest, fluids and simple painkillers help. If symptoms worsen instead, go down.
- Loss of coordination — cannot walk a straight line heel to toe
- Confusion, odd behaviour, or unusual drowsiness
- Severe headache that does not respond to painkillers
- In effect, AMS that has become neurological
What to do: Descend immediately, whatever the hour and whatever the plan. HACE kills quickly and descent is the treatment. Do not let the person walk down alone or wait for morning.
- Breathlessness at rest, not just on exertion
- A dry cough that turns wet, sometimes pink or frothy
- Chest tightness and a racing heart
- Extreme fatigue and a marked drop in performance
- Can occur with no headache and no AMS at all
What to do: Descend immediately. HAPE can develop in someone who felt fine and is a leading cause of altitude deaths. Descent is the treatment; supplemental oxygen helps but does not replace going down.
The field test: Ask them to walk a straight line heel to toe for about five metres. Someone who cannot do it, or who has to put a foot out to steady themselves, is showing ataxia — treat that as HACE until proven otherwise and descend.
How to use
- Enter your starting and target altitudes for a safe night-by-night sleeping profile with rest days built in.
- Or paste the sleeping altitudes you already have planned and see which nights break the rate rule.
- Read the recognition section before you go, not after someone starts feeling ill.
Frequently asked questions
How fast can I go up?
Above about 8,000 feet, increase your sleeping altitude by no more than roughly 1,600 feet a night and take a rest day for every 3,300 feet gained. Below 8,000 feet the rules do not really bite, which is why the first day of a trip can be a big jump.
Why sleeping altitude specifically?
Because that is what your body acclimatizes to. You can go considerably higher during the day and come back down — that is what "climb high, sleep low" means, and it genuinely helps. What matters is where you spend the night.
Does being fit help?
No, and this surprises people. Fit young people get altitude sickness at least as often as anyone else, partly because they ascend faster. Susceptibility is largely individual and fairly consistent, so if you have had trouble before, plan for it again.
What is the difference between AMS, HACE and HAPE?
AMS is headache plus other symptoms and means stop ascending. HACE is AMS gone neurological — loss of coordination, confusion — and HAPE is fluid in the lungs, causing breathlessness at rest. Both of those kill, both are treated by descending immediately, and HAPE can strike someone with no headache at all.
Is this medical advice?
No. It is trip-planning arithmetic. Altitude illness can kill within hours and no web page can assess anybody. If symptoms are getting worse the answer is to descend immediately, at night if necessary, and get real medical help.
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