Magic Mile Calculator
Predicted 5K, 10K, half-marathon and marathon times from a one-mile time trial — the Galloway "magic mile".
Run one mile as fast as you can after a warm-up.
How the magic mile calculator works
Run one mile as fast as you can after a warm-up. Jeff Galloway’s rule scales the per-mile pace: 5K pace is the mile time plus 33 seconds, 10K pace is the mile × 1.15, half-marathon pace × 1.2 and marathon pace × 1.3. Multiply each pace by the distance and you have a realistic finishing time for a properly trained runner.
Formula: per-mile pace: 5K = mile + 33 s; 10K = mile × 1.15; half = mile × 1.2; marathon = mile × 1.3
Worked examples
| Inputs | Predicted marathon | Note |
|---|---|---|
| 8:00 mile | 4:32:41 | 4:32:41 marathon |
| 6:30 mile | 3:41:33 | 3:41:33 marathon |
| 10:00 mile | 5:40:51 | 5:40:51 marathon |
FAQFrequently asked questions
How do I run the magic mile?
Warm up for ten minutes, then run one mile (four laps of a standard track) as hard as you can hold evenly, and jog to cool down. Repeat every few weeks and use your best time.
How accurate are the predictions?
They assume you have trained for the distance — long runs approaching the race length for a marathon. An untrained runner will not hold the predicted marathon pace, however fast the mile.
Why is the marathon factor 1.3 but the 5K just 33 seconds?
Endurance falls away with distance: the longer the race, the bigger the gap from your mile pace. Galloway derived the factors from thousands of runners’ results.
What pace should I train at?
Galloway suggests long runs about two minutes per mile slower than the predicted marathon pace, and easy days slower still.
Where these figures come from
- World Handicap System — Rules of Handicapping — the score differential and handicap index formula
- International Cricket Council — Playing Conditions — over structure and run-rate definitions
- Major League Baseball — Official Rules — the published definitions for baseball statistics
Last checked: September 2026. Formulas follow the governing bodies where one publishes them — the World Handicap System for golf, the ICC playing conditions for cricket run rates.