Pace, speed & race time prediction (Riegel formula)
Your run
Pick a common race distance, or enter your own below.
Enter your finish time:
Your pace & speed
Pace (per km)
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Pace (per mile)
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Speed (km/h)
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Speed (mph)
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Predicted times at other distances
Race time predictions (Riegel formula) assume similar training and conditions across distances — treat them as a rough guide, not a guarantee, especially across very different distances.
How it works
Pick a distance from the presets, or enter a custom one.
Enter your finish time. We divide time by distance to get your pace in both min/km and min/mile, plus your speed in km/h and mph.
We predict times at other distances using the Riegel formula, a standard method for estimating race performance at a new distance based on a known result.
Race predictions assume proportional endurance across distances. Real results depend on training specificity, pacing strategy, terrain, and weather.
Frequently asked questions
Pace is your time divided by distance, usually expressed as minutes per kilometer or minutes per mile. Enter the distance you ran and your finish time, and this calculator does the division for you.
It uses the Riegel formula: T2 = T1 × (D2/D1)^1.06, a widely-used method that predicts finish time at a new distance based on a known performance at another distance. It assumes similar training and conditions.
It's reasonable for predicting times across moderate distance differences (like 5K to 10K), but becomes less reliable for very different distances (like 5K to marathon), since endurance and pacing strategy matter more at longer distances.
There's no single "good" pace — it varies enormously by age, fitness level, and experience. Many beginners run in the 6-8 minutes per km (10-13 min/mile) range, but your own pace over time is the most useful benchmark.