Running Pace Calculator
Enter a distance and time to calculate your pace, speed and predicted race times.
Fill in the form and hit calculate to see your results here.
Your pace
Predicted race times
Predictions use the Riegel formula and assume similar training and conditions across distances.
Pace vs. speed
Pace (minutes per km or mile) is the standard way runners talk about effort, while speed (km/h or mph) is more familiar from treadmills and cycling — we calculate both.
How race predictions work
The Riegel formula uses your current fitness at one distance to estimate performance at another, based on how endurance typically scales with distance.
Why predictions aren't guarantees
Race predictions assume consistent training and similar conditions — pacing, terrain, weather and race-day nerves all affect the actual result.
The formulas
# Pace Pace = time / distance # Speed Speed = distance / time # Race prediction (Riegel formula) T2 = T1 × (D2 / D1) ^ 1.06
Common questions
They're a reasonable estimate for similar distances, but accuracy drops the further the prediction is from your input distance — a 5K time predicts a 10K better than a marathon.
The pace and speed math works for any steady-effort activity, but the race time predictions are specifically calibrated for running endurance curves.
Endurance drops off non-linearly over longer distances, which the Riegel formula accounts for — but factors like fuelling and pacing strategy matter more at marathon distance than this formula can capture.
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