How it works
Most race calculators use a single formula and give you a single number. RaceCast blends multiple models, adjusts for your training and race-day conditions, and gives you an honest confidence range.
Multiple models, one prediction
We use three well-established prediction models from sports science — each with different strengths. Rather than showing you three conflicting numbers, RaceCast intelligently blends them based on your data. The more information you provide, the smarter the blend.
Personalized to you
Enter a second race and RaceCast learns how your body handles distance — not just the average runner. Add your training details and the prediction accounts for your weekly mileage, longest run, and whether you do speed work. Every input makes the prediction more accurate.
Real-world adjustments
A prediction is only useful if it reflects race day. RaceCast adjusts for factors that other calculators ignore:
Honest confidence range
Every prediction includes a range — not just a single number. The range widens when there's more uncertainty (like predicting a marathon from a 5K) and narrows when we have more data to work with. No false precision.
Built on research
Our models and adjustments are grounded in peer-reviewed sports science research, including work by Riegel, Cameron, Daniels & Gilbert, Vickers & Vertosick, and others. The specific implementation — how we blend, weight, and adjust — is our own.
RaceCast was built by a runner who got tired of calculators that didn't account for the real world — training load, heat, hills, or the difference between a first-timer and a veteran. We built the tool we wished we had before our own race days.
Built by a runner, for runners.