Race Time Predictor

Build a prediction from your own race history instead of relying on one generic conversion. Add a few recent, all-out results for the best estimate.

Personalized endurance curve Weather-aware Marathon reality check

HOW IT WORKS

Your races teach the model how you slow down as distance increases.

The calculator fits a weighted time-versus-distance curve to your results. Recent races and true race efforts matter more. Difficult courses and hot weather can be normalized so one rough day does not define your fitness.

1. RACE HISTORY

Race results

Preloaded with Taya’s recent races. Checked races are used in the current-fitness prediction.

Quick add:

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2. TARGET

Choose what you want to predict

Target distance Expected course Typical weekly mileage Used for the research-based marathon check. How should older races count?

Optional target weather

Race date Start time City or postal code Wet-bulb temperature °F

Add at least one complete race result

With one result, the tool uses a standard endurance curve. With multiple distances, it starts learning yours.

PREDICTED FINISH

Half Marathon

--:--:--

Pace / mile --:--

Pace / km --:--

Model confidence --

Your fatigue factor 1.07

Races used 0

Distance coverage --

RACE EQUIVALENTS

Predicted times by distance

Distance	Finish time	Pace / mile	Likely range

YOUR CURVE

How your results compare

Dots are your weather- and course-normalized race results. The line is the fitted prediction.

Your races Prediction

What is happening behind the scenes?

The main prediction uses a power-law relationship between time and distance, then fits the fatigue factor to your own included races. The fit is weighted so recent, all-out races count more, and it is gently pulled toward a standard value when there is not enough distance variety to estimate your curve reliably.

For marathons, the tool also calculates a separate estimate from a model developed using 2,303 recreational runners. That model combines one or two non-marathon race results with typical weekly mileage because simple race-conversion formulas often predict marathon times that are too fast.

Historical weather comes from Open-Meteo. When wet-bulb temperature is available, the tool applies a conservative heat normalization based on published endurance-event findings. Weather and course adjustments are estimates, not guarantees.

Riegel endurance model Recreational runner study Weather and endurance review Weather data documentation

Use this as a planning estimate, not a promise. Training specificity, fueling, pacing, course profile, weather and how the day actually goes still matter.