Three-Way Solver
Select what you want to solve for, then fill in the other two fields:
Distance presets:
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h : mm : ss
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Pace
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Distance
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Time
Split Table
Complete the solver above to generate splits.
Race Finish Predictor
Enter a known race result to predict finish times for all standard distances using the Riegel formula (T2 = T1 × (D2/D1)1.06). Results are estimates — actual performance varies with training, course, and conditions.
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Pace Conversion Reference
Common paces in min/km, min/mi, km/h, and mph — plus projected finish times for standard race distances.
| min/km | min/mi | km/h | mph | 5K | 10K | Half | Marathon |
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Frequently Asked Questions
Multiply your min/km pace by 1.60934. For example, 5:00 min/km = 5 × 1.60934 = 8:03 min/mile. The conversion table above and the pace widget show this instantly in both directions.
A good 5K pace depends on experience. Beginners often aim for 7–9 min/km (11–14 min/mi), finishing in 35–45 min. Intermediate runners target 5–7 min/km (8–11 min/mi), finishing in 25–35 min. Competitive club runners aim for under 4 min/km (6:26 min/mi), finishing under 20 min. Elite male runners finish under 14 minutes.
A 4-hour marathon requires a pace of 5:41 per km (9:09 per mile). Set the distance to Marathon and time to 4:00:00 in the solver above to get exact splits. The key is consistent effort — most runners slow in the final 10K, so training to maintain pace under fatigue is critical.
The Riegel formula (Peter Riegel, American Scientist, 1977) predicts performance at a new distance from a known result: T2 = T1 × (D2/D1)^1.06. The exponent 1.06 accounts for the endurance fatigue factor — the longer the race, the harder it gets proportionally. For a 25:00 5K, the formula predicts approximately 52:20 for a 10K and 1:55:30 for a half marathon.
A negative split means running the second half of a race faster than the first. It is recommended for marathons and half marathons because starting conservatively delays glycogen depletion and lets you finish strong. The split table tool above lets you plan a negative split: set a "slower" buffer for the first half, and the table shows your adjusted per-km/mile targets.