Last updated September 16, 2026
AMS Altitude Sickness Risk Calculator: Check Your Ascent Plan
Use the calculator to review the parts of an itinerary that most strongly affect acute mountain sickness risk—especially sleeping altitude, rate of ascent, recent acclimatization and your own response to comparable altitude in the past.
No Calculator Can Tell You Whether You Will Get AMS.
The CDC Yellow Book states that there is no simple screening test that reliably predicts an individual traveler’s altitude-illness risk. This tool is therefore best used as an itinerary risk screen: it helps you notice modifiable factors in the ascent plan, not produce medical clearance or a guaranteed personal probability.
A lower-risk itinerary does not mean you cannot become sick. A higher-risk itinerary does not mean you will. Symptoms on the mountain always matter more than a pre-trip score.
Emergency rule: confusion, loss of coordination/ataxia, severe deterioration, or shortness of breath at rest can signal life-threatening high-altitude illness. Stop ascending, descend urgently when feasible, and seek medical help.
AMS Altitude Sickness Risk Calculator
Enter your planned ascent profile. Use the output to identify itinerary features worth changing or discussing with a clinician—not as a substitute for symptoms, judgment or professional medical advice.
The Three Risk Categories Used in Current CDC Guidance
The CDC frames AMS risk primarily around prior altitude illness, the first night’s sleeping altitude and the rate of sleeping-altitude gain. The categories below are a planning framework, not individualized medical predictions.
Gradual Entry + Gradual Ascent
A traveler starting low, sleeping below roughly 2,750 m on the first high-altitude night, and then increasing sleeping altitude conservatively has a more favorable ascent profile.
- No history of serious altitude illness.
- First night at a more moderate elevation.
- Sleeping-altitude gains stay conservative.
Faster Entry or Prior Moderate AMS
Risk rises when the first sleeping altitude is higher, the itinerary compresses acclimatization, or the traveler has previously experienced more significant AMS on a comparable ascent.
- Faster sleeping-altitude gain.
- First night around 2,750–3,400 m.
- Prior moderate or severe AMS.
Rapid Ascent or Prior HACE/HAPE
Flying or driving rapidly to a high sleeping altitude, then continuing upward without adequate acclimatization time, creates a high-risk ascent profile. A history of HACE or HAPE also warrants specialist medical planning.
- First sleeping altitude above roughly 3,400 m.
- Large gains without adequate acclimatization days.
- History of HACE or HAPE.
Four Inputs Worth Paying Attention To
These factors are more useful than trying to predict altitude illness from fitness, age alone, or a single oxygen-saturation number.
Where You Sleep Drives the Acclimatization Load.
Day hikes higher can be useful, but sleeping altitude is the more important planning variable. A short visit to a summit and descent to a lower camp is physiologically different from moving the sleeping elevation to that same height.
“Too High, Too Fast” Is the Classic Preventable Risk.
Current CDC and WMS guidance commonly uses about 500 m of sleeping-altitude gain per day above 3,000 m, with additional acclimatization days during continued ascent. Routes and terrain can make real itineraries less tidy, which is why the pattern matters more than one perfect number.
Your Own History Helps—When the Comparison Is Fair.
How you handled a previous trip is useful only when the altitude and ascent rate were reasonably similar. Feeling fine during a slow week at 3,500 m does not prove you will tolerate a rapid ascent to 5,000 m.
Recent Exposure Can Change the Starting Point.
Recent time spent at altitude can provide useful acclimatization. The value depends on how high you went, how long you stayed and how much time has passed before the new trip.
Fitness helps you climb. It does not immunize you against AMS.
Very fit athletes can develop altitude illness. Use fitness planning for the workload of the mountain, and altitude planning for acclimatization; they are related expedition problems but not interchangeable ones.
Why the Route Plan Can Matter More Than the Summit Name
A mountain’s summit elevation alone does not describe the altitude risk. The sequence of sleeping elevations often matters more.
| Itinerary pattern | What changes | Why it matters | Better planning question |
|---|---|---|---|
| Fly directly from low elevation to a high city | Large first-night jump | The body receives little time to begin acclimatizing before sleep. | Can I stage lower for 1–3 nights first? |
| Trek slowly to the same final altitude | More nights during ascent | Acute acclimatization develops over the first several days. | Are the sleeping-altitude gains conservative? |
| Climb high, return lower to sleep | High daytime exposure without permanently moving camp | A high point reached briefly is different from sleeping at that altitude. | What is my actual sleeping profile? |
| Compress a route to save a day | Larger sleeping-altitude gain | Shortening the trip can remove the very acclimatization time that made the original itinerary workable. | Which acclimatization night am I deleting? |
| Repeat a mountain after recent altitude exposure | Starting acclimatization may be better | Recent exposure can be protective, but the effect fades and is not a guarantee. | How recent and how comparable was the exposure? |
Do Not Use a Pre-Trip Risk Score to Diagnose AMS
AMS is diagnosed from the situation and symptoms after a recent ascent, not from a pre-trip questionnaire. The 2018 Lake Louise score is a symptom-scoring system used in altitude research and clinical context; it is not a pre-trip prediction test.
The current Lake Louise framework centers on symptoms such as headache, gastrointestinal symptoms, fatigue/weakness and dizziness/light-headedness. Sleep disturbance was removed from the 2018 score because it was not specific enough to AMS.
Likewise, a pulse oximeter can provide useful context at altitude, but a single oxygen-saturation number cannot tell you that a person is safe to keep ascending. Symptoms, trend, altitude, device quality, cold fingers and individual variation all matter.
Turn the Score Into an Itinerary Decision
The useful next step is not worrying about a color or percentage. It is deciding whether the ascent plan should change.
Keep the Conservative Structure.
Do not remove acclimatization days merely because the tool looks reassuring. Monitor symptoms anyway, especially after each meaningful increase in sleeping elevation.
Look for the Specific Problem.
Identify whether the issue is first-night altitude, rapid sleeping-altitude gain, lack of rest days, or a history of significant altitude illness. Fix the itinerary where possible and discuss medical prevention with an appropriate clinician.
Do Not Treat Medication as a Substitute for Time.
High-risk ascent profiles deserve a more conservative plan. Medication can be useful in selected cases, but it does not make reckless ascent rates safe or replace descent when severe illness develops.
When the Mountain Changes the Plan
A calculator is useful before departure. Once you are at altitude, the rule changes: actual symptoms and function matter more than the pre-trip estimate.
Mild AMS-type symptoms after ascent: do not ascend higher while symptoms persist. Rest, reassess and follow the plan agreed with your guide or clinician.
Worsening symptoms: a deteriorating climber should not be pushed upward simply to preserve an itinerary or summit schedule.
HACE warning signs: confusion, altered mental status or loss of coordination are medical emergencies. HAPE warning signs: breathlessness at rest, marked weakness, cough and significant deterioration can signal pulmonary edema. These conditions require urgent descent when feasible and medical treatment.
For the full symptom and treatment framework, use the dedicated Altitude Sickness Guide and Altitude Illness Treatment Guide.
The Calculator Is One Piece of the Altitude System
A good result still needs a realistic itinerary, symptom knowledge and conservative decision rules.
Acclimatization Schedule Builder
Lay out sleeping elevations and see where the itinerary makes its biggest jumps.
Core guideAltitude Acclimatization Explained
Understand what changes in the body during the first several days at altitude.
PlanningHow to Acclimatize
Turn the physiology into a practical route and sleeping-altitude strategy.
SymptomsComplete Altitude Sickness Guide
AMS, HACE and HAPE recognition, prevention principles and escalation rules.
DecisionWhen to Turn Around
Build a conservative decision framework before summit pressure distorts judgment.
Medical referenceAltitude Illness Treatment Guide
Understand why stopping ascent, descent and medical evaluation matter when illness develops.
Interactive AMS Risk Calculator: Estimate Your AMS, HACE & HAPE Risk
For a real trip, plug in the planned sleeping profile from the mountain itinerary and then compare the result with the mountain-specific acclimatization guidance.
Kilimanjaro Progression Plan
Use route length and sleeping elevations to understand why a longer itinerary can matter.
5,636 mPico de Orizaba Progression
Review how Mexico volcano acclimatization can be staged before the summit attempt.
6,961 mAconcagua Progression Plan
See how a long expedition uses carries, camps and acclimatization days at extreme altitude.
AMS Risk Calculator Questions
The page intentionally avoids promising a precise personal probability because current medical guidance does not support that level of prediction.
Can an altitude sickness calculator predict whether I will get AMS?
No. Current CDC guidance says there is no simple screening test that reliably predicts an individual outcome. The calculator is most useful for identifying itinerary features associated with higher or lower risk, such as first-night sleeping altitude and rate of ascent.
What are the biggest risk factors for acute mountain sickness?
The most useful planning variables are the sleeping altitude, the rate at which sleeping altitude increases, recent acclimatization, and your prior response to a similar altitude and ascent profile. Individual susceptibility still varies substantially.
Does being very fit prevent altitude sickness?
No. Fitness helps with the physical workload of climbing, but it does not reliably protect against AMS. A highly trained person who ascends too quickly can still become ill.
Can I use my pulse oximeter to decide whether it is safe to continue?
Do not use a single pulse-ox number as medical clearance to continue ascending. Oxygen saturation falls with altitude and readings are affected by cold hands, movement, device quality and individual variation. Symptoms and clinical context matter more than one number.
How fast should sleeping altitude increase above 3,000 meters?
Current CDC and WMS guidance commonly uses about 500 meters of sleeping-altitude gain per day above 3,000 meters, with additional acclimatization days during continued ascent. Treat that as a planning framework rather than a guarantee of safety.
What should I do if AMS symptoms develop?
Do not ascend higher while symptoms persist. If symptoms worsen, or if confusion, loss of coordination or shortness of breath at rest develops, descend urgently when feasible and seek medical care. Severe altitude illness can be life-threatening.
Should the calculator tell me whether to take acetazolamide?
No. The calculator can identify a more concerning ascent profile, but medication decisions depend on medical history, contraindications, itinerary and clinician judgment. Discuss prevention medication with a clinician familiar with altitude medicine.
Primary Guidance Used for This Page
This rebuild intentionally uses current authoritative altitude-medicine sources rather than relying on the calculator’s original scoring language.
- CDC Yellow Book 2026 — High-Altitude Travel and Altitude Illness: CDC high-altitude guidance.
- Wilderness Medical Society — Acute Altitude Illness 2024 Update: WMS 2024 altitude summary.
- Lake Louise AMS Score Consensus Committee (2018): PubMed record for the revised Lake Louise AMS Score.
Medical limitation: Global Summit Guide is an educational travel and mountaineering resource, not a medical service. People with cardiopulmonary disease, pre-existing hypoxemia, obstructive sleep apnea, sickle-cell trait or other significant medical conditions should discuss high-altitude travel with an appropriate clinician before departure.
Build an Ascent Your Body Has Time to Adapt To.
Use the calculator to expose the itinerary. Then protect the acclimatization days, monitor symptoms honestly, and be willing to stop climbing when the mountain gives you information the spreadsheet could not.
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Global Summit Guide is an independent mountaineering resource founded in 2026. The team combines first-hand trekking and climbing experience with in-depth research and professional health and nutrition review to help climbers choose objectives, prepare properly, and stay safe.
Health, altitude, and nutrition content is reviewed by Taylor Ludlow (Registered Nurse) and Brigg Hoopes (Nutritionist).
What We Don't Know Yet
Mountain information changes quickly. This box explains the limits of what this page can responsibly promise.
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Mountaineering, rock and ice climbing, glacier travel, and high-altitude activity are inherently dangerous and can result in serious injury or death. The information on Global Summit Guide is provided for general informational and educational purposes only and is not a substitute for professional instruction, qualified guiding, proper equipment, or your own judgment and experience.
Route conditions, weather, snowpack, permits, regulations, and hazards change constantly and may differ from what is described here. Details may be incomplete, out of date, or contain errors. Always verify current information with local authorities, certified guides, and official sources before making any decision in the mountains.
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