Summit · 8 September 2026
The oxygen arithmetic of 5,000 metres
Altitude is a number before it is a feeling. Air pressure falls with height, oxygen falls with it, and the body adapts at a rate that has been measured for decades. The Altitude Simulator applies the arithmetic to your nights; this is the arithmetic.

Summit · India
Ladakh and Zanskar
Leh sits at 3,500 metres in a desert valley between the Himalaya and the Karakoram: monasteries on rock spurs, the highest motorable passes on earth, and in winter the Chadar, a trek along the frozen Zanskar river.
Best window: June to September for the passes and treks; January and February for the ChadarDays needed: 8 to 10
Ladakh is a high desert wedged between the Himalaya and the Karakoram, Buddhist by culture, Indian by passport, and dry enough that its rivers matter more than its rain. Leh sits at 3,500 metres and the passes climb past 5,300; monasteries stand on rock spurs above the valleys, and in winter the Zanskar river freezes into a road of ice that the villages have walked for centuries. Everything here is about altitude, and the trip that works is the one that respects it.
What the model says
June to September is the season for the passes and the treks: highs in the low twenties in Leh, nights near freezing higher up, almost no rain. January and February are the Chadar, at minus twenty. The Altitude Simulator is the tool for this page: it models the flight from Delhi at 200 metres to Leh at 3,500 and shows why the first two days are rest days and the passes come on day three at the earliest.
What the ground says back
The cost is the lowest of the summit realm by a distance, and the infrastructure of guesthouses, agencies and drivers in Leh is excellent. The Nubra and Pangong loop is the classic week; the Markha valley trek adds five days on foot over a 5,260 metre pass. Roads are rockfall roads and the drivers know them. The Chadar is changing as a road is built up the gorge, and the honest description is that it is still extraordinary and shorter than it was.
Days
Eight days for Leh, Nubra and Pangong with the rest days. Ten adds a short trek. A fortnight adds the Markha valley or the drive out over the Manali road, which is one of the great high roads on earth.
A sample day
- 06:30Prayers at Thiksey monastery, the horns echoing down the valley
- 08:00Breakfast of butter tea and tsampa, the sun already hard at 3,500 m
- 10:00Drive up the Khardung La, the road cut into scree, 5,359 m at the top
- 12:00Down into the Nubra valley, sand dunes with double-humped camels
- 15:00Diskit monastery and the giant Buddha looking up the valley
- 17:30Camp at Hunder, apricot trees, the river loud in the dark
- 19:30Dinner of thukpa, the stars over the Karakoram
- 21:00Early sleep; the altitude makes every day a long one
A sample plan · 9 days
- Day 1Fly into Leh, do nothing, drink water, walk to the market slowly.
- Day 2Second rest day: Shanti Stupa, Leh Palace, an evening at Thiksey.
- Day 3Over the Khardung La to Nubra, camp at Hunder.
- Day 4Turtuk village near the border, back to Nubra.
- Day 5Over the Wari La or via the Shyok to Pangong lake, night at Spangmik.
- Day 6Back to Leh via the Chang La.
- Day 7Rest and prep, or the Markha valley trek for five days.
- Day 8Markha valley: Skiu, Markha, Hankar, over the Kongmaru La at 5,260 m.
- Day 9Return to Leh, fly to Delhi.
- 10.1hJan
- 10.9hFeb
- 12hMar
- 13hApr
- 14hMay
- 14.4hJun
- 14.2hJul
- 13.4hAug
- 12.3hSep
- 11.2hOct
- 10.3hNov
- 9.9hDec
What can go wrong
- ▲▲▲AltitudeLanding at 3,500 m from sea level; acute mountain sickness is common and the passes are 5,000 m higher up. Two rest days are the rule, not a suggestion.
- ▲▲▲ColdWinter at minus twenty on the Chadar; summer nights below freezing on the treks.
- ▲▲RoadsThe Khardung La and the Manali road are landslide and rockfall roads; drivers know when to stop.
- ▲▲RemotenessHelicopter evacuation exists from Leh; from Zanskar it does not.
Getting there
Fly Delhi to Leh, an hour and a quarter that jumps from 200 to 3,500 metres, which is why the first two days are rest. The Manali and Srinagar roads open from June to October for the overland version. Treks and the Nubra and Pangong valleys are arranged from Leh with local agencies.
Hub Leh airport, flights from Delhi
Permits Inner Line Permits for Nubra, Pangong and the border valleys, issued in Leh in a day; the Chadar has its own registration and medical check.
Avoid April and November: the roads are closed by snow and the flights by weather, and the treks are neither open nor frozen.
Questions people ask
How bad is the altitude?
Leh at 3,500 m is one of the highest airports you can fly into from sea level. Most people have a headache the first night, and the ones who drive up the passes on day two are the ones the clinic sees. Two rest days and slow walking solve most of it.
Is the Chadar still possible?
A road is being built up the gorge and the ice season is shorter than it was. Trips still run in January and February, registered and medically checked, and the trek is now partly on the ice and partly on the new road.
When can I drive in?
The Manali and Srinagar roads open in late May or June and close with the first heavy snow in October or November.
Field Notes
Summit · 8 September 2026
The oxygen arithmetic of 5,000 metres
Altitude is a number before it is a feeling. Air pressure falls with height, oxygen falls with it, and the body adapts at a rate that has been measured for decades. The Altitude Simulator applies the arithmetic to your nights; this is the arithmetic.
Summit · 25 August 2026
Training for a trek in twelve weeks
Fitness for a trek is built in weeks and lost in weeks, and the plan that works is boring: three walks a week, one long one at the weekend with the loaded pack, stairs for the descents, and a lighter week every fourth. The Training Simulator builds it backwards from your date.
Method · 11 September 2026
Choose the month, not the place
Most trips are planned in the wrong order: place first, dates second, weather last. Reverse it and half the disappointments on this site disappear before booking.
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