Running Pace Calculator

Pace is time per unit distance (minutes per kilometer or mile) — the number runners actually think in during a race. Speed is distance per unit time (km/h or mph) — the number more commonly used for cycling or driving. This calculator shows both from the same input.

Each predicted distance (5K, 10K, half marathon, marathon) is multiplied by your calculated pace-per-unit-distance — this assumes you could hold the exact same pace across the full race distance, which is a simplification; in practice, pace naturally varies with distance (most runners slow down somewhat as race distance increases), so treat longer predictions as optimistic rather than guaranteed.

A half marathon is officially 21.0975 km (13.1094 miles) and a full marathon is 42.195 km (26.2188 miles) — these odd-looking figures come from the historical/Olympic standardization of the marathon distance, not a rounding choice in this calculator.

The pace/speed math works for any steady-distance activity, but the built-in finish-time predictions (5K, 10K, half marathon, marathon) are running-specific distances — for other sports, use the pace and speed results directly rather than the prediction table.