Two races with similar characteristics are never completely identical. And two editions of the same event can be influenced by external factors such as wind, rain, or trail conditions.

Our statistical model draws on thousands of historical data points to compare all athletes against one another and measure their expected performance in a race against the performances actually observed on race day.

This allows us to factor out any external conditions that may have influenced the event and build a comprehensive, reliable picture of each athlete's performance.

Final times in Trail Running are influenced by many factors such as terrain technicality, heat, wind, rain, altitude, time of day, etc.

Our experience shows that it is not possible to quantify the technical difficulty of a race, which is why we have developed a calculation method based on a statistical analysis of the results and runners of each race, drawing on our database of over 11.4 million individual results.

The same level of technical difficulty is applied equally to all runners in a race for each edition of that race. This method has two major advantages: It allows us to account for all factors that can affect race time.

If conditions slow a race down, we can identify it in the results.

Our database and scoring system continuously improve as we collect more race data.

Recent results are considered more important than older results when calculating the UTMB Index.

When a result is more than 12 months old, a negative weighting is applied, which reduces its value.