Convert your race times between elevations using research-backed formulas
Enter your race details and click "Calculate" to see your converted time
This calculator uses research from Dr. Jack Daniels and Wehrlin & Hallén's studies on altitude's effect on VO₂max. At altitude, the reduced air pressure means less oxygen reaches your muscles, slowing performance by approximately 1.5-2% per 1,000 feet above 3,000 feet elevation.
Use this calculator to set realistic pace expectations when racing at altitude, understand the true fitness value of high-altitude training runs, and compare performances across different elevations. Dr. Daniels suggests adding 4-5 seconds per mile for every 1,000 feet above 3,000 feet for threshold and interval training.
The calculator assumes no effect below 3,000 ft (914 m), then roughly 1.6% slower for every 1,000 ft above that. Longer races are affected slightly more, so a marathon loses more than a 5K at the same altitude.
The calculator uses a threshold of about 3,000 ft (914 m). Below that, the effect on endurance races is too small to matter. Above it, the thinner air means less oxygen reaches your muscles and your pace drops.
Much less. Short races rely less on oxygen delivery, so the calculator applies a smaller adjustment to races under about 5 minutes. True sprints can even be slightly quicker at altitude because the air is thinner.
Two to three weeks at altitude reduces the impact noticeably, although it does not disappear completely. Some runners adapt much better than others, so treat the converted time as a guide.
Jack Daniels suggests slowing threshold and interval paces by about 4 to 5 seconds per mile for every 1,000 ft above 3,000 ft.
Choose to convert from altitude to sea level, enter your race distance, time and altitude, and the calculator shows what that performance is worth at sea level. You can also convert the other way to set a realistic target for a race at altitude.
Iten in Kenya is about 7,874 ft, Mexico City 7,349 ft, Font-Romeu in the French Pyrenees 5,910 ft, Boulder in Colorado 5,430 ft and Albuquerque 5,312 ft. For comparison, the summit of Ben Nevis is 4,413 ft. Pick a preset in the calculator or enter any altitude in feet or metres.