How accurate are race time predictions?

The Riegel formula is accurate to within 2-3% for well-trained runners racing between 5K and marathon distances. Accuracy decreases for ultra distances and for runners who are undertrained for the target distance.

Should I use my goal time or conservative estimate?

For your first race at a new distance, use the conservative estimate. For experienced racers with solid training, the predicted goal time is appropriate. Only use the aggressive estimate if conditions are perfect and you are exceptionally well-prepared.

Does weekly mileage affect my predicted time?

Yes. Higher weekly mileage improves endurance, particularly for longer distances. A runner averaging 80 km/week will likely perform better at the marathon than a 40 km/week runner with the same 5K time.

How recent should my race result be?

Use a result from the last 6-8 weeks for the most accurate prediction. Older results may not reflect your current fitness, especially if your training has changed significantly.

RunCalcs

Goal Time Calculator — Set a Realistic Race Goal

Set a realistic race goal time based on a recent race result and your training.

Recent Race Hours

Time in hours

Recent Race Minutes

Time in minutes

Recent Race Seconds

Time in seconds

Recent Race Distance

Distance measurement

Target Race Distance

Distance measurement

Weekly Training Distance

Distance measurement

Weeks of Structured Training

Enter the weeks of structured training

How We Calculate This

Goal Time Calculation

The calculator uses the Riegel formula with training adjustments:

Predicted Time = Recent Time x (Target Distance / Recent Distance)^1.06

The base prediction is then adjusted for weekly training volume and weeks of preparation. A conservative estimate adds 3% and an aggressive estimate subtracts 3% to give you a range of realistic goals.

Frequently Asked Questions

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Peak Week Calculator

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Corral Calculator

Estimate your race corral placement based on predicted time.

Aid Station Calculator

Calculate when you will reach each aid station during your race.

Last updated: February 2026

All calculations are estimates. Always consult a coach or medical professional for personalised training advice.