| Landing site | Elevation | Effective oxygen | Of a sea-level breath |
|---|---|---|---|
| Kala Patthar | 18,192 ft5,545 m | 10.4% | 50% |
| Everest Base Camp | 17,598 ft5,364 m | 10.6% | 51% |
| Manaslu Base Camp | 15,750 ft4,801 m | 11.4% | 55% |
| Gosaikunda | 14,370 ft4,380 m | 12.1% | 58% |
| Annapurna Base Camp | 13,550 ft4,130 m | 12.5% | 60% |
| Hotel Everest View | 12,729 ft3,880 m | 12.9% | 62% |
| Kyanjin Gompa | 12,697 ft3,870 m | 12.9% | 62% |
| Lo Manthang | 12,500 ft3,810 m | 13% | 62% |
| Pathibhara Temple | 12,444 ft3,793 m | 13.1% | 62% |
| Syangboche | 12,402 ft3,780 m | 13.1% | 63% |
| Muktinath | 12,172 ft3,710 m | 13.2% | 63% |
| Lukla | 9,334 ft2,845 m | 14.7% | 71% |
| Jomsom | 8,976 ft2,736 m | 15% | 72% |
| Kathmandu | 4,390 ft1,338 m | 17.8% | 85% |
| Pokhara | 2,712 ft827 m | 18.9% | 91% |
| Tumlingtar | 1,600 ft488 m | 19.7% | 94% |
| Nepalgunj | 540 ft165 m | 20.5% | 98% |
| Biratnagar | 236 ft72 m | 20.7% | 99% |
Altitude and oxygen
Free calculator
How high is it, and what is left to breathe?
Five of the helipads on this platform are above 12,500 ft. Here is what the air is doing at each of them — computed from the surveyed elevation against the standard atmosphere, not looked up.
No sign-upSurveyed elevationsStandard atmosphere
18
Landing sites
18,192ft
Highest — Kala Patthar
50%
Of a sea-level breath there
8
Above 12,500 ft
Oxygen is 20.9% of the air at every altitude a helicopter reaches. What changes is the pressure: at 5,500 m it is about half of sea level, so one breath holds about half the oxygen — the same as breathing 10.5% oxygen at the coast. The mixture never thins; the atmosphere does.
Every landing site
Ranked by height
Highest first. The oxygen column is the share of a sea-level breath, computed from each site's surveyed elevation.
What the numbers mean
Thin air, in plain terms
Two of these are physics and the third is the reason it matters commercially.
- Is there less oxygen at high altitude, or is the air just thinner?
- The air is thinner. Oxygen makes up 20.9% of dry air at every altitude a helicopter reaches — what falls is the pressure, so each breath contains fewer molecules of everything, oxygen included. At 5,500 m the pressure is about half what it is at sea level, so a breath holds about half the oxygen, which is the same as breathing roughly 10.5% oxygen at the coast.
- How is the effective oxygen percentage at altitude calculated?
- It is the oxygen fraction of air, 20.9%, multiplied by the air pressure at that height as a fraction of sea-level pressure. The pressure comes from the International Standard Atmosphere, the model every aircraft performance chart is drawn against: pressure falls as (1 − 0.0000225577 × height in metres) raised to the power 5.25588. The result is the oxygen percentage sea-level air would need to give you the same amount per breath.
- Does flying to a high helipad affect you differently from trekking there?
- The exposure is different in both length and speed. A helicopter reaches a Himalayan landing site in tens of minutes and is usually on the ground for well under an hour, where a trek takes days and sleeps at height. Neither is a statement about whether a particular person is affected — that depends on the person, and it is a question for a doctor rather than a calculator.
- Do Nepali helicopter operators carry oxygen on board?
- Several do, and it is listed as an inclusion on the routes where it applies rather than assumed. Supplemental oxygen on board appears on the operator's own offer for the route, so it is visible before booking on the route page. Tell the flight desk if anybody in your party has a heart or lung condition, and it will be part of how the flight is planned.
- Why does altitude decide how many passengers a helicopter can carry?
- Thinner air gives a rotor less to work with, so the aircraft's maximum weight falls as the landing site gets higher — and the empty aircraft and its fuel come out of that allowance first. A five-seat helicopter is often a two- or three-seat helicopter at a Himalayan helipad, whatever the cabin holds. That calculation is what the payload planner does.
The same thin air decides who can come: the payload planner works out how many of your party an aircraft can lift to a given helipad, and the flight-time calculator gives the distance and the climb to it. Which month to go is a separate question — the season calendar says what each operator publishes as in season.
Flying with elderly parents or young children?
Leave a number. A dispatcher rings back and plans the ground time, the oxygen and the landing site around who is actually on board — it is the part of a Himalayan flight that gets decided on the phone.