8 weeks · 2 sessions/wk
Strength for runners
A more efficient stride, tougher calves and tendons and fewer injuries, without cutting miles.
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Race Time Predictor: 5K, 10K, Half Marathon and Marathon
Enter a recent race result (for example, your last 10K) and we'll estimate how long the other distances would take you if you train for them.
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How the prediction works
We use the Riegel formula: T2 = T1 × (D2 ÷ D1)1.06. The 1.06 exponent reflects that your pace slows slightly as the race gets longer. It's the formula most widely used by coaches and sports watches.
When it's accurate and when it isn't
- It's most accurate between similar distances (5K to 10K, 10K to half marathon).
- For the marathon it's optimistic if you haven't done long runs of 28-32 km (17-20 miles): add 3-5%.
- Use a result from the last 2-3 months on a flat course.
Frequently asked questions
How long will a half marathon take me if I run a 50-minute 10K?
Around 1:50:30, at about 5:14 min/km (8:25 min/mile), if you've trained for long distances.
Is it reliable to predict a marathon from a 10K?
It gives you a good reference, but the marathon depends heavily on training volume. Treat it as your best-case scenario.
Recommended gear
- GPS running watchLogs your runs and predicts race times.
- Energy gelsEssential for runs longer than 60-75 minutes.
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Exercises that help you improve
Week-by-week training programs
8-week plans with sets, reps and progression, built for your sport. Includes a downloadable PDF.
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