Marathon Time Calculator
Predict marathon time from recent race performances
How to Use
- Enter your recent race time in HH:MM:SS or MM:SS format
- Enter the distance of your recent race
- Select distance units (kilometers or miles)
- Choose from common race distances with quick select buttons
- Click calculate to see your predicted marathon time
- Review multiple prediction methods and required pace
Marathon Time Prediction Formulas
Marathon time prediction uses mathematical formulas based on your recent race performances. These formulas account for the relationship between distance and running performance, helping estimate your marathon potential.
The calculator uses three established methods: Riegel Formula (conservative, good for endurance), Cameron Formula (balanced for most runners), and Purdy Formula (optimistic for well-trained athletes).
Riegel Formula
The Riegel Formula, developed by Peter Riegel, is one of the most widely used running prediction methods. Formula: T2 = T1 × (D2/D1)^1.06
- Uses a 1.06 exponent to account for fatigue over longer distances
- Generally provides conservative predictions
- Most accurate for endurance-trained runners
- Works best when predicting longer distances from shorter races
Cameron Formula
The Cameron Formula offers a balanced approach to time prediction. Formula: T2 = T1 × (D2/D1) × [0.1 + 0.9 × (D1/D2)^0.5]
- Accounts for both distance ratio and speed maintenance
- Provides moderate predictions suitable for most runners
- Considers the relationship between race distances
- Less conservative than Riegel but more realistic than Purdy
Purdy Formula
The Purdy Formula is often more optimistic, developed for competitive runners. It uses a logarithmic approach to account for performance degradation.
- Typically produces faster predicted times
- Most suitable for well-trained, competitive runners
- Accounts for training adaptation and race experience
- May be too optimistic for recreational runners
Using Marathon Predictions
- Use predictions as training goals, not absolute targets
- Consider recent training consistency and fitness level
- Account for course difficulty and weather conditions
- Factor in your race day experience and mental preparation
- Use the most conservative prediction for safe goal setting
- Adjust goals based on how training progresses
- Consider multiple predictions to establish a time range
- Remember that marathon performance has many variables
Training for Predicted Marathon Time
- Build weekly mileage gradually over 12-16 weeks
- Include long runs at predicted marathon pace
- Practice race day nutrition and hydration strategies
- Incorporate tempo runs and speed work for leg turnover
- Run at least one 18-20 mile long run before race day
- Practice pacing during training runs
- Include back-to-back long runs on weekends for fatigue adaptation
- Taper properly in the final 2-3 weeks before the marathon
Frequently Asked Questions
- How accurate are marathon time predictions?
- Predictions are typically within 5-10% of actual marathon times for most runners. Accuracy depends on training consistency, race conditions, course difficulty, and individual physiology. Use predictions as guidelines rather than guarantees.
- What's the best recent race to use for prediction?
- Use your most recent race from the past 4-6 weeks. Ideally, use a distance between 10K and half marathon for the most accurate predictions. Avoid using very short races (under 5K) or races from several months ago.
- Which prediction formula should I trust most?
- For most runners, the Riegel Formula provides the most reliable conservative estimate. Well-trained endurance athletes might find Cameron more accurate, while elite runners might align with Purdy. Consider all three to establish a realistic time range.
- Can I predict marathon time from a 5K race?
- While possible, predictions from 5K races are less accurate than from longer distances. The greater the distance difference between your recent race and marathon, the more potential for prediction error. 10K to half marathon distances work best.
- How should I adjust predictions for hilly courses?
- Add 2-5 minutes to your predicted time for moderately hilly courses, and 5-10+ minutes for very hilly or mountainous courses. Consider elevation gain, terrain type, and your experience with similar course profiles when adjusting expectations.