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What it is
Altitude acclimatization is the process of giving your body time to adapt as you go higher, where the air holds less oxygen. Above about 2,500 metres, climbing too fast commonly causes headache, nausea, poor sleep, and tiredness, and in serious cases fluid can build up in the lungs or brain, which is a medical emergency. A planned, gradual ascent is the main defence.
The widely used guideline is simple: above 2,500 metres, raise your sleeping altitude by no more than 500 metres per day, and take a rest day after each 1,000 metres gained. Sleeping altitude matters more than the highest point you reach during the day, because your body adapts overnight.
How to use it
Enter the altitude where you will first sleep and the altitude where you want to sleep at the end of the trip, both in metres. Press Calculate and you get a day-by-day table: each day’s sleeping altitude and whether it is a climbing day or a rest day, plus the total trip length.
Use the table as the skeleton of your itinerary, then fit real camps, huts, or towns to it. If no camp exists at the planned height, sleep lower rather than jumping higher: the schedule is a ceiling, not a target you must hit exactly.
Worked example
Starting at 1,500 metres and aiming to sleep at 4,500 metres gives a schedule of about nine days. The first jump reaches 2,500 metres, then the 500-metre rule takes over, with rest days built in after each 1,000 metres gained above 2,500 metres. Rushing the same gain into four or five days would break the guideline on almost every day.
That difference is the whole point: the plan looks slow on paper, but it is the speed at which most people can actually enjoy the trip and stay well.
How to read your result
Each row is one day and one sleeping altitude. Climb days end at a new, higher camp. Rest days keep the same sleeping altitude, which lets your body catch up even though you are not gaining height. The trip length counts every day, including rest days, because rest days still cost time, food, and money.
If your trip must be shorter than the schedule, change the destination, not the rule: a lower target you reach safely beats a higher target reached sick.
Common mistakes
The dangerous mistake is treating a rest day as wasted time and skipping it to keep up with a group or a fixed flight home. Another is climbing high and sleeping high on the same day, which removes the protection of sleeping low. A third is ignoring early symptoms and climbing anyway, hoping they pass: they usually get worse with height.
Limits
This planner is an educational estimator, never medical advice. It uses one common guideline, but individual risk varies with age, fitness, previous altitude illness, and speed of travel, and some people need a slower schedule or preventive medicine prescribed by a doctor. Altitude sickness is serious: if you feel ill, stop climbing, rest, and descend if symptoms do not improve, and get help fast for confusion, breathlessness at rest, or a cough with frothy fluid.
Questions people ask
Can I climb higher during the day than I sleep?
Yes, and it often helps. Day trips above your sleeping altitude, then returning to sleep lower, are the classic climb-high-sleep-low pattern, but they do not replace rest days.
What if there is no camp at the planned altitude?
Sleep lower. The schedule gives maximum sleeping gains, so a lower camp is always acceptable, while a higher jump breaks the guideline.
Do fit people acclimatize faster?
Not reliably. Fitness helps you walk further, but it does not protect against altitude sickness, and fit people sometimes climb too fast because they feel strong at first.
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