Heat and altitude pace adjustment
This heat and altitude pace calculator adjusts a cool-weather, sea-level pace for hot temperatures and high elevation, using a simple rule-of-thumb model. Enter the pace you'd run in mild conditions near sea level, plus the temperature and altitude you'll actually face, and see how much slower to expect and why, useful for planning race pacing on a hot summer morning or a trail run at elevation.
Adjusted pace
5:30/km
This is a rule-of-thumb estimate, not a physiological model. Individual heat and altitude tolerance varies widely.
How it works
Heat above roughly 15°C adds a percentage penalty to pace, on the order of 1 percent per degree Celsius above that threshold, capped at 15 percent, reflecting the added cardiovascular strain of dissipating heat during exertion.
Altitude above roughly 1000 metres adds a separate penalty, growing with elevation, reflecting reduced oxygen availability at altitude. Below that threshold the model adds nothing, since the effect on unacclimatized runners is generally small at lower elevations.
Both penalties are added together and applied to your entered pace to produce the adjusted figure. This is a simplified rule of thumb, not a validated physiological model, and real-world results vary with humidity, acclimatization, hydration and individual heat tolerance.
Frequently asked questions
How much does heat slow down running pace?
As a rough rule of thumb, expect pace to slow by roughly 1 percent for each degree Celsius above about 15°C, up to a cap of around 15 percent in extreme heat. Actual slowdown depends heavily on humidity and acclimatization, so treat this as a starting estimate rather than a precise prediction.
At what altitude does running pace slow down?
Effects are generally small below roughly 1000 metres of elevation for most runners, then grow with additional altitude as oxygen availability drops. Full acclimatization to altitude typically takes one to several weeks, so a pace run shortly after arrival will feel harder than the same effort weeks later.
Should I trust this calculator for race pacing decisions?
Use it as a rough guide, not a guarantee. It applies a simplified additive rule of thumb rather than a physiological model validated across individuals, and factors like humidity, wind, hydration and personal heat tolerance can shift the real effect meaningfully in either direction.
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These values are training estimates. They are not medical advice.
Overload logs conditions alongside every run
Overload records the weather and elevation for every logged run, so you can see how heat and altitude actually affected your pace over time. Free on iOS and Android.