AltitudeAheadPlanning acclimatization days
General ascent recommendations and why an extra day can make a difference.
General recommendations
Widely used guidance for travel above about 3,000 m: avoid going directly from low altitude to a high sleeping altitude in one day; once above about 3,000 m, increase your sleeping altitude by no more than about 500 m per day; and plan an extra acclimatization day for about every 1,000 m of sleeping-altitude gain, or every three to four days.
These are general recommendations for groups of people, not guarantees for an individual. Some people get altitude illness even on a gradual schedule.
What an acclimatization day is
An acclimatization day is a day on which you don't sleep higher than the night before. You can rest or take a short hike higher and come back down to sleep.
AltitudeAhead counts every night that doesn't go higher as an acclimatization night, whether or not you marked it as a rest day. A marked rest day that still raises your sleeping altitude isn't counted.
How AltitudeAhead counts
AltitudeAhead adds up sleeping-altitude gain above 3,000 m since your last acclimatization night. When that has reached about 1,000 m and the next day goes higher again, it suggests reviewing whether an extra day fits. A descent resets the count; climbing back up counts again.
If your plan has no flagged days, it only means none of these general rules matched. It doesn't mean your plan is safe for you.
Building flexibility into your trip
Plan buffer days. A schedule without spare days creates pressure to keep going when you or someone in your group doesn't feel well. With reputable operators, ask how they handle altitude illness, extra days and descent.
General information, not medical advice. If you have symptoms at altitude, don't go higher. See the medical disclaimer.
