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Calcimator

Altitude Acclimatization Calculator

Plan a safe acclimatization schedule for high-altitude mountaineering. Calculate recommended ascent rate, rest days, and altitude sickness risk based on Wilderness Medical Society guidelines.

Inputs

ft
ft
ft

Results

Recommended Days

11 days

Max Daily Altitude Gain

400 m/day

Rest Day Every800 m gained
Rest Days Needed3 days
Climbing Days8 days
Total Altitude Gain3,000 m
AMS Risk Score54/100
Risk LevelHigh
How to Use This Calculator
  1. Enter your starting altitude in meters (e.g., 2500 m for a trailhead base camp).
  2. Input your target altitude in meters — the highest point you plan to sleep at.
  3. Set your current acclimatized altitude, or leave at 0 if you are coming from sea level.
  4. Review the recommended Acclimatization Days and maximum Daily Altitude Gain (m) based on WMS guidelines.
  5. Note the Rest Days Required and schedule them into your itinerary every ~1000 m of gain above 3000 m.
  6. Check the AMS Risk Level — if rated High or above, plan a longer acclimatization profile before attempting your target.

How the result changes with Target Altitude

Target AltitudeRecommended DaysMax Daily Altitude Gain
9801 days800 m/day
3,1802 days500 m/day
5,82012 days400 m/day
8,02026 days300 m/day

What each input means

Starting Altitude
Altitude of your base camp or starting point in meters above sea level.
Target Altitude
Summit or highest camp altitude in meters. Everest base camp is 5,364m; summit is 8,849m.
Current Acclimatized Altitude
The altitude you are currently acclimatized to from recent exposure. If coming from sea level, enter 0.

What each result means

Recommended Days
Total days including climbing days and rest days for safe acclimatization.
Max Daily Altitude Gain
Maximum recommended sleeping altitude gain per day based on target altitude zone.
Rest Day Every
Take a rest day (no altitude gain) for every this many meters of altitude gained.
Rest Days Needed
Number of dedicated rest days built into the acclimatization schedule.
Climbing Days
Number of days with upward progress (excluding rest days).
Total Altitude Gain
Total vertical gain from starting altitude to target altitude.
AMS Risk Score
Acute Mountain Sickness risk score from 0 (minimal) to 100 (extreme). Based on altitude, gain rate, and acclimatization status.
Risk Level
Qualitative risk assessment: Low (0-20), Moderate (21-40), High (41-60), Very High (61+).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Starting Altitude = 2500, Target Altitude = 5500, Current Acclimatized Altitude = 2000 = 3 input(s) provided
  2. Calculate Recommended Days
    Recommended Days
    11 = 11
  3. Calculate Max Daily Altitude Gain
    400 = 400
  4. Calculate Rest Day Every
    800 = 800
  5. Calculate Rest Days Needed
    Rest Days Needed
    3 = 3

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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