Magic Mile Calculator — Jeff Galloway Race Time Predictor
Run a 1-mile time trial (the Magic Mile), then use Jeff Galloway's multipliers to predict realistic finish times for the 5K, 10K, half marathon and marathon.
min
sec
≈ 5:43 min/km • 5K finish: 28:31
- 1
Magic Mile time in minutes
8 = 8 - 2
Predicted 5K pace
8 × 1.15 = 9.20Galloway factor ×1.15 converts the 1-mile effort to a sustainable 5K pace (min/mi).
How does this calculator work?
Run a hard 1-mile time trial (the Magic Mile). Multiply by 1.15 for your 5K pace/mi, 1.18 for 10K, 1.20 for half marathon, 1.30 for marathon. Then multiply pace × race distance in miles for the predicted finish time. Repeat monthly to track fitness gains.
Formula
How this is calculated
Jeff Galloway's Magic Mile is a structured 1-mile time trial used to predict race paces without the wear of a full race. You run one mile at your best sustainable effort — not an all-out sprint but close to it — and record the time in minutes and seconds. That single number anchors all of your race predictions.
Galloway's published multipliers convert the Magic Mile (MM) time into a predicted pace per mile for each standard race distance: multiply MM by 1.15 for a 5K pace, 1.18 for a 10K pace, 1.20 for a half-marathon pace, and 1.30 for a marathon pace. Then multiply the resulting pace by the race distance in miles (3.1, 6.2, 13.1, or 26.2) to get the predicted finish time. The larger multipliers for longer races account for the extra physiological cost of sustained effort at marathon distances.
The predictions assume you train appropriately for the target race, use a run-walk-run strategy if needed, and that conditions (weather, terrain, fatigue) are similar to your time trial. The marathon multiplier in particular is conservative — most runners need the extra buffer. Galloway recommends repeating the Magic Mile monthly to track fitness progress and update predictions.
Frequently asked questions
After a proper warm-up, run exactly one mile at your best sustainable effort — the pace you could hold for a hard workout, not a full-out 400m sprint. Record the time in minutes and seconds. Cool down well and avoid running it on a hilly course.
The multipliers are based on Galloway's data from tens of thousands of runners. For well-trained runners with appropriate base mileage, they are typically accurate to within a few minutes for shorter races and 5–15 minutes for a marathon. Heat, hills, and inadequate training increase the error.
Yes. Multiply your MM time by 1.15 to get your predicted 5K pace per mile, then multiply that by 3.1 to get the finish time. For example, an 8:00 MM gives a 5K pace of 9:12 min/mi and a 5K time of about 28:31.
TG we-Calculate Editorial Team. (2026). Magic Mile Calculator — Jeff Galloway Race Time Predictor [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/magic-mile-calculator
TG we-Calculate Editorial Team. "Magic Mile Calculator — Jeff Galloway Race Time Predictor." TG we-Calculate. 2026. https://we-calculate.com/calculator/magic-mile-calculator.
TG we-Calculate Editorial Team, "Magic Mile Calculator — Jeff Galloway Race Time Predictor," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/magic-mile-calculator
@misc{wecalculate_magic_mile_calculator, title = {Magic Mile Calculator — Jeff Galloway Race Time Predictor}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/magic-mile-calculator}}, year = {2026}, note = {TG we-Calculate} }
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