What is the Half Marathon Pace Calculator?
A half marathon covers exactly 21.0975 kilometers (13.1094 miles). This calculator converts your target or actual finish time into an average running pace — expressed as minutes and seconds per kilometer and per mile — plus your average speed. It is useful for planning race-day effort, setting training targets, and comparing performances across distances.
How to use it
Enter your finish time in hours, minutes and seconds. The calculator divides the total time by the half marathon distance to give your average pace. For example, a 1:45:00 finish means you ran each kilometer in roughly the same average time throughout the race.
The formula explained
First the time is converted to seconds: Total seconds = hours × 3600 + minutes × 60 + seconds. Pace per kilometer is then Total seconds ÷ 21.0975, and pace per mile is Total seconds ÷ 13.1094. Speed is the distance divided by the time in hours.
Worked example
Suppose you finish in 1 hour 45 minutes (6300 seconds). Pace per km = 6300 ÷ 21.0975 ≈ 298.61 s/km ≈ 4:59 min/km. Pace per mile = 6300 ÷ 13.1094 ≈ 480.57 s/mi ≈ 8:01 min/mi. Average speed ≈ 21.0975 ÷ 1.75 h ≈ 12.06 km/h.
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