Race Time Predictor
Curious what you could run at a distance you've never raced? This predictor takes your existing performances and estimates what you're capable of at any standard race distance — from 100 meters to the full marathon. It's the core tool behind RacePotential, built on multiple validated performance models.
How it works
The race time predictor uses a blend of Riegel's scaling formula, VDOT-based estimation, critical speed modeling, and empirical speed-ratio analysis. Each model captures different aspects of running performance — raw speed, aerobic capacity, fatigue resistance, and event-specific factors. By combining them with appropriate weights, the predictor produces more reliable estimates than any single model alone.
Training advice
Race prediction works best when you have recent, all-out efforts to base it on. A time trial from 4-6 weeks ago is more useful than a race from last year. For the most accurate predictions, enter times from at least two different distances. And remember — predictions show potential, not guarantees. Proper pacing, nutrition, and race-day conditions all affect whether you reach that potential.
Frequently asked questions
How does race time prediction work?
Race prediction models use the mathematical relationship between speed and distance. As distance increases, pace slows at a predictable rate that depends on your physiological profile. By measuring this rate from known performances, the model extrapolates to untested distances.
Is the Riegel formula accurate?
The Riegel formula is a solid starting point, but it tends to overestimate performance at extreme distances. Our predictor improves on Riegel by blending it with VDOT and critical speed models, especially for distances beyond 10K.
Why do I need multiple race times?
Multiple times let the model understand your personal speed-endurance profile. Some runners lose more time as distance increases (speed-dominant), while others hold pace better (endurance-dominant). Two or more times reveal which type you are.
Can I predict sprint times from distance times?
Predictions between very different event types (e.g., 5K to 100m) are unreliable because they depend on entirely different physiological systems. The predictor works best within related distance ranges.
Related tools
- 5K Time Predictor
- Marathon Time Predictor
- VDOT Calculator
- Running Pace Calculator
- How Running Times Scale by Distance