Tools · Race Pace
Race pace predictor
Enter a recent race. Get predicted times for every common distance plus your training paces. Uses the Riegel formula — the most widely validated race predictor in running.
Race predictions
- 1 mile6:294:02 /km
- 5K21:354:19 /km
- 10KYour race45:004:30 /km
- Half marathon1:39:174:42 /km
- Marathon3:27:014:54 /km
- 50K4:07:494:57 /km
Training paces
Based on your current 5K race fitness.
- Easy / long runConversational, 75–80% of weekly volume5:32 /km
- Marathon paceSlightly slower than threshold4:58 /km
- Tempo / thresholdComfortably hard, 20–40 min4:37 /km
- 10K paceHard, sustainable for 30–50 min4:27 /km
- 5K / intervalRace effort, 3–5 min repeats4:19 /km
- VO2 max / repetition1500m–mile pace, short intervals4:03 /km
Better predictions from real training data.
Gneta tracks your Garmin race predictor over time, plots it against your actual fitness trend, and lets the AI coach advise when you're race-ready.
How this works
The Riegel formula
Peter Riegel published this equation in 1977 after analyzing hundreds of race times across distances. The 1.06 exponent accounts for the gradual slowdown as race distance grows.
T₂ = T₁ × (D₂ / D₁)^1.06It assumes you're similarly trained for both distances. A 5K specialist predicting a marathon will see a time that's optimistic — they lack the endurance base. A marathoner predicting a 5K will see a time that's pessimistic — they lack speed. The closer your race distances, the better the prediction.
Frequently asked questions
How accurate is a race pace predictor?
The Riegel formula is accurate within 1–3% for well-trained athletes predicting similar-distance races (e.g. 10K → half marathon). Accuracy degrades with larger distance jumps (5K → marathon) and for athletes whose endurance outpaces their speed, or vice versa. Use it as a starting point, not gospel.
What is the Riegel formula?
Peter Riegel's 1977 formula: T2 = T1 × (D2 / D1)^1.06. The 1.06 exponent accounts for the fact that you slow down slightly per kilometer over longer races. It remains one of the most widely used and tested race predictors despite being almost 50 years old.
Can I use a treadmill or training run as input?
Only if it was a maximal effort over the stated distance. Race performance reflects pacing, fueling, and mental effort that regular training runs don't. Time trials and races are what the formula is designed for.
Why are my training paces different from what this predicts?
Training paces here are based on your current race fitness. If you train harder or easier than these paces feel, trust how you feel over the formula. These paces assume healthy recovery; in a high-stress week, easy pace should drift 15–20 seconds slower.
Does this work for trail or ultra running?
Not directly. Riegel assumes flat, consistent terrain. For trail races, add 10–30% to the predicted time depending on elevation gain and technicality. Ultras (50+ miles) break the formula entirely — fueling and pacing dominate.
Should I trust this or my Garmin race predictor?
Garmin's race predictor uses your actual training data — VO2 max trend, recent pace distribution, lactate threshold — and is usually more accurate. The Riegel formula is the right tool when you have one recent race time and want a quick estimate. Gneta syncs and visualizes Garmin's predictions over time so you can see fitness trending.
Keep exploring
Race the numbers, not the clock.
Gneta pulls your Garmin race predictor, VO2 max trend, and training load together so you know when you're actually ready.
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