Running Pace Calculator
Calculate running pace and speed, then predict race times for 5K, 10K, half and full marathon distances.
🔒 Runs entirely in your browser — nothing is uploadedPace, speed and the conversion math
Running pace is simply time divided by distance. If you cover 10 km in 50 minutes, your pace is 5:00 per kilometer. This calculator converts your total time into seconds, divides by the distance in kilometers and miles, and formats the result as minutes and seconds per unit. Speed is the inverse relationship: speed = distance ÷ time, shown here in both km/h and mph. Switching the distance unit only changes how the input is read; the underlying conversion uses 1 mile = 1.609344 km.
Pace and speed are two views of the same effort. A 5:00/km pace equals 12 km/h and about 7.46 mph, or roughly 8:03 per mile. Seeing all of them together makes it easy to compare treadmill settings, GPS watch readouts and race plans that use different units.
Predicting other race distances
To estimate how a result at one distance translates to another, the tool uses Peter Riegel's endurance formula: T₂ = T₁ × (D₂ ÷ D₁)^1.06. The exponent 1.06 captures the fact that pace slows slightly as races get longer, because you cannot hold a short-distance pace over a marathon. From your single entry it predicts finish times for 5K, 10K, the half marathon and the full marathon, along with the matching per-kilometer pace for each.
How to use the predictions
These predictions assume similar terrain, weather and that you are reasonably trained for the target distance. Hills, heat, wind, fueling and your endurance base can all move the real number, so treat them as informed targets rather than guarantees. Build up distance gradually and let training, not just a formula, set your race goals. This page is for general information only and is not medical or coaching advice. All calculations run locally in your browser and nothing is uploaded.
How to use
- Enter distanceType the distance you covered and choose kilometers or miles.
- Enter your timeAdd the hours, minutes and seconds it took to finish.
- Read pace and predictionsSee pace per km and mile, speed, and predicted times for common race distances.