Running Pace & Race Time Predictor
Convert split paces (min/km & min/mile) and predict 5K, 10K, Half, and Full Marathon times using Pete Riegel’s fatigue equation.
Input Parameters
MetricInstant Biometric Computation
Speed: 12.4 km/h · Est. VO2 Max: 37.4 ml/kg/min
Pete Riegel Race Time Predictions
Export to Fitness Logs & Spreadsheets
Save this calculation for your training log: Apple Notes, Notion, Obsidian, Google Sheets, or Excel.
How This Calculator Works & Mathematical Formula
Pete Riegel Endurance Equation:
T2 = T1 × (D2 / D1)1.06
Where T1 is your baseline race time, D1 is baseline distance, D2 is target distance, and 1.06 is the empirical fatigue exponent across human aerobic events from 1,500m to ultra-marathons.
Standard Physiological Guidelines & Scientific References
Clinical Society Guidelines
- World Athletics Physiological Evaluation Models
- Riegel PS. Athletic records and human endurance. American Scientist. 1981;69(3):285-290.
- Daniels J. Daniels' Running Formula (4th Edition). Human Kinetics, 2021.
Peer-Reviewed Citations
- Vickers AJ, Vertosick FT. An empirical study of race times in recreational marathon runners. BMC Sports Sci Med Rehabil. 2016;8:26.
- Noakes TD. Lore of Running (4th Edition). Human Kinetics, 2003.
Formula Limitations, Safety Guidance & Doctor Consultation
Formula Limitations & Population Assumptions
•The Riegel prediction assumes adequate aerobic base training for the target distance. Attempting a marathon based purely on 5K pace without high weekly mileage will result in glycogen depletion ("the wall").
•Environmental factors including heat index, humidity, elevation, and terrain grade alter pacing requirements by 3-15%.
When to Consult a Physician
Always consult a licensed medical professional before implementing significant changes to your caloric intake, fasting routine, hydration targets, or strenuous exercise programming. Seek immediate medical evaluation if you experience unexplained chest discomfort, irregular heartbeats, shortness of breath, dizziness, syncope, or if you have pre-existing cardiovascular, metabolic, renal, or endocrine conditions.
Not medically reviewed. The results and estimates generated by this calculator are derived strictly from published population formulas and sports science research. They are intended for general athletic education and personal informational purposes only, and must never be construed as clinical diagnosis, medical prescription, or specialized healthcare advice.
Frequently Asked Questions (4 Technical Inquiries)
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