Calculate your running pace, speed, and predicted finish times for 5K, 10K, half marathon, and marathon distances.
Calculate My Pace ↓Get your pace, speed, and predicted times for other race distances.
Predicted times at this fitness level
Based on the Riegel formula — an estimate, not a guarantee.
Most of your weekly running volume, roughly 80%, should be done at an easy, conversational pace. Counterintuitively, spending most of your training time slower — not faster — builds the aerobic base that ultimately allows faster race-day paces.
Once a solid aerobic base is established, adding one weekly session of intervals or tempo running teaches your body to sustain faster paces for longer. This is the remaining 20% of training volume that directly targets race pace improvement.
A commonly cited guideline is increasing weekly mileage by no more than 10% per week, to reduce injury risk while still progressively building fitness. Rapid increases in volume are one of the most common causes of running injuries.
Running some training miles at your actual goal race pace helps your body and mind learn what that effort level feels like, making it easier to hold steady during the race itself rather than starting too fast and fading.
Your pace is calculated simply by dividing your total time by your total distance. The predicted times for other distances use the Riegel formula, a widely cited method in exercise science: T2 = T1 × (D2 ÷ D1)1.06, where T1 and D1 are your known time and distance, and T2 is the predicted time for a new distance D2. This formula accounts for the fact that pace naturally slows somewhat as distance increases, rather than assuming a flat linear relationship.
This prediction assumes broadly similar training and conditions across distances, which won't always hold true. A strong 5K runner without any endurance-specific training may not hit their Riegel-predicted marathon time without dedicated long-run training, since marathon performance depends heavily on endurance-specific adaptations that a 5K time alone doesn't fully capture. Treat these predictions as a reasonable starting estimate for goal-setting, not a guarantee of race-day performance.
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