Altitude Performance Calculator
Aerobic performance drops roughly 1% per 100 m above 1000 m. A 300 W sea-level FTP can drop to 255 W or lower at Leadville (3100 m) without acclimatization. This tool calculates your Oxygen-Corrected Power Protocol: adjusted zones, pace, and an acclimatization recovery timeline.
Based on Wehrlin and Hallen (2006) and Chapman et al. (1998). Enter your training and race elevation, your sport, and days at altitude to get corrected targets.
Enter your training and race elevation to see your altitude adjustment.
Training zones?
Heart Rate Zone Calculator
Build all 5 heart-rate zones from your age and resting HR, with Zone 2 front and center.
Hot race?
Heat-Adjusted Pace Calculator
Convert your goal pace for real temperature and dew point. Many mountain races are also hot.
How much time do you lose racing at altitude?
Aerobic performance drops about 1 percent for every 100 m (330 ft) of elevation above roughly 1,000 m, before any acclimatization. For a sea-level runner arriving cold, that turns an 8:00 per mile effort into roughly 8:27 at 5,000 ft and over 9:20 at 8,000 ft. The loss is larger the higher and the more aerobic the event, and acclimatizing for two to three weeks recovers about half to most of it.
| Race elevation | Aerobic loss (unacclimatized) | Pace add on an 8:00 mile |
|---|---|---|
| 5,000 ft (1,524 m) | ~5% | +27 sec/mi |
| 6,000 ft (1,829 m) | ~8% | +43 sec/mi |
| 7,000 ft (2,134 m) | ~11% | +61 sec/mi |
| 8,000 ft (2,438 m) | ~14% | +81 sec/mi |
| 10,000 ft (3,048 m) | ~20% | +124 sec/mi |
Gross figures for a sea-level-trained athlete on arrival, from the same 1 percent per 100 m model the calculator uses. Enter your home and race elevations and your days to acclimatize above for your adjusted pace and power.
Altitude performance calculator FAQ
How much slower do you run at altitude?
Above 1000 to 1500 m, aerobic performance drops roughly 1% per 100 m of additional elevation gain in trained athletes (Wehrlin and Hallen, 2006). At Leadville (3100 m / 10,200 ft), a sea-level runner can expect 10 to 15% slower aerobic pace on arrival. After 14 days of acclimatization, that gap closes to 5 to 8%. The exact figure depends on your training elevation, fitness level, and individual response, which varies more than average-population models predict.
How does altitude affect VO2max?
Altitude reduces VO2max because the partial pressure of oxygen in the air drops with elevation, which limits oxygen delivery to working muscles even when breathing rate and heart rate increase. At 2500 m (8200 ft), VO2max is roughly 10 to 12% lower than at sea level for well-trained athletes. This translates directly to reduced sustainable power and pace at any aerobic intensity, which is why sea-level FTP numbers are unusable at race altitude without correction.
How long does it take to acclimatize to altitude?
Altitude acclimatization is a multi-phase process. In the first 1 to 3 days, ventilation and heart rate increase as acute compensation. Over 1 to 2 weeks, plasma volume expands and 2,3-DPG in red blood cells increases, improving oxygen unloading. By 14 days, roughly 50% of the initial performance deficit is recovered. Full red blood cell mass increases (the primary long-term adaptation) take 3 to 4 weeks. If you cannot get 14+ days, arriving within 24 hours of the start is often better than arriving 3 to 7 days before, when acute symptoms are worst.
Should I use my sea-level FTP at Leadville?
No. Leadville (100 miles, 3100 m average elevation) is one of the most altitude-challenged race venues in ultra-endurance sport. A 300 W sea-level FTP typically drops to 255 to 270 W on race day without acclimatization, or 270 to 285 W with 2 to 3 weeks of altitude camp. Racing to sea-level power outputs at Leadville is a reliable way to blow up in the first half. Use this calculator to set adjusted zones, then hold those targets conservatively for the first 30 minutes until your HR response tells you what you can sustain.
Does altitude affect cycling more than running?
On a percentage basis, the VO2max and aerobic power reduction is the same for both sports at the same elevation. However, altitude affects cycling differently in practice because cycling is largely an aerobic-power sport at continuous high intensity, while running introduces more mechanical factors and race-specific pacing. Cyclists racing at altitude typically see a larger absolute power drop because they sustain higher percentages of VO2max for longer durations. Trail runners in mountain ultras also cope with elevation gain on course, which compounds the atmospheric altitude effect.
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See also: how to race at altitude, including pacing, acclimatization, and when to arrive.
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