How to Use PredictMyRun for Accurate Race Predictions

PredictMyRun is designed to help runners estimate their performance across different race distances based on their previous results. Our calculator uses the Riegel formula, a well-established method for predicting race times. Here's how to get the most accurate predictions for your upcoming races.

Understanding the Riegel Formula

The Riegel formula is based on the observation that as race distance increases, pace typically slows down in a predictable pattern. It uses the following equation:

T2 = T1 × (D2 ÷ D1)^k

Where:

• T1 is your time for a known distance
• D1 is the known distance
• T2 is the predicted time
• D2 is the race distance you're predicting
• k is a fatigue factor (typically 1.06 for most runners)

Getting the Most Accurate Predictions

Use Recent Race Results

For the most accurate predictions, use a recent race result as your baseline. Performance from 6+ months ago may not reflect your current fitness level.

Use Similar Distance Races

Predictions are generally more accurate when the known and predicted distances are closer together. For example, a 10K time will predict a half-marathon time more accurately than a 5K time would predict a marathon.

Consider the Course Profile

Our calculator assumes similar terrain and elevation between races. If your baseline race was flat but your target race is hilly, you may need to adjust expectations.

Factor in Weather Conditions

Extreme weather can significantly impact performance. Hot, humid conditions typically slow runners by 1-2% for every 5°F above 60°F.

Example Use Case

Let's say you recently ran a 10K race in 50:00 (50 minutes) and want to predict your marathon time:

1. Enter 10 in the distance field and select kilometers
2. Enter 50:00 in the time field
3. Select marathon (42.195 km) as your target distance
4. The calculator will predict your marathon time using the Riegel formula

The predicted time gives you a good starting point for setting realistic goals and planning your race strategy.

Beyond the Calculator

Remember that while mathematical predictions are helpful, they don't account for all factors that affect race performance, such as:

• Training specificity for the target distance
• Nutrition and hydration strategy
• Mental preparedness
• Race day conditions

Use the PredictMyRun calculator as a guide, then adjust based on your personal experience and training history. With regular use, you'll get better at understanding how the predictions relate to your actual performance.

Happy running and racing!