How much slower at altitude?
Racing above 2,000 feet slows a runner who lives near sea level by about 1% for every 1,000 feet higher: about 3% in Denver.
A recent race in good weather. Aiming for a goal instead? The last line of the answer covers it.
Town elevations. Or type any altitude.
Load it to use its course's average altitude.
Anywhere up to 2,000 ft counts as near sea level.
| The day before | This estimate. |
|---|---|
| 2 to 4 days before | Usually the worst time to arrive: sleep and breathing are at their hardest. We don't put a number on it. |
| 5 days to 2 weeks before | Past the worst of it, though your body is still adapting. We don't put a number on it. |
| 2 to 3 weeks or more | Your body adapts and gets part of the cost back. We don't put a number on it. |
Best bet: arrive within 24 hours of the start, or at least 5 days early. Two weeks or more is better still.
Only the first row is modelled. The others are general guidance, not a calculation.
How we got this
Nothing up to 2,000 ft (610 m), then about 1% per 1,000 ft (300 m) above it, for a runner who lives near sea level. 5,280 ft is 3,280 ft above that line: about 3.3%.
Anywhere up to 2,000 ft (610 m) counts as near sea level. If you live higher, enter it and we take out what your home altitude already costs.
It's a conservative estimate, at the low end of the research. A loaded race uses the course's average altitude, not the start.
Questions
- How much does altitude slow a race?
- For a runner who lives near sea level and arrives the day before: nothing up to 2,000 feet (610 m), then about 1% of pace per 1,000 feet (300 m) above it. Denver, at 5,280 feet, is about 3.3% slower: a 4:00 marathon becomes about 4:08. This is a conservative estimate, at the low end of the published research.
- I live at altitude. Does it still apply?
- Less of it does. Enter where you live and the calculator takes out what your home altitude already costs by the same rule, so a Boulder runner racing in Denver sees no cost, and a Denver runner racing in Mexico City sees about 2%. Anywhere up to 2,000 feet counts as near sea level.
- Should I arrive early?
- Arrive within 24 hours of the start, or at least 5 days early; two weeks or more is better still. The number here is for arriving the day before. Arriving 2 to 4 days ahead is usually the worst choice, with poorer sleep and harder breathing. From about 5 days you are past the worst of it, and two to three weeks lets your body adapt and get part of the cost back. We don't put a number on those: the research doesn't give one we trust for a single runner.
- Which altitude does a loaded race use?
- The course's average altitude along the mapped route, not the start line. A race that starts high and descends is charged for where it is run, not where it begins.