HesapHanem

Running Pace Calculator

From distance and time: pace per km, average speed, and projected times for 5K, 10K, half-marathon and marathon.

How it is calculated

Enter the distance in kilometres and the time as hours, minutes and seconds. The tool converts the time to total seconds and computes pace = total seconds / distance (shown as minutes:seconds per km) and speed = distance / total seconds × 3600 in km/h. Both distance and total time must be above zero.

It then projects finish times at the same constant pace: time = pace × race distance for 5 km, 10 km, the half marathon (21.0975 km) and the marathon (42.195 km), rounded to whole seconds. This assumes you hold an even pace throughout. In practice most runners slow down over longer distances, so a marathon projection from a 5K pace is optimistic. Miles are not supported, so convert to km first (1 mile ≈ 1.609 km).

Worked example

You ran 10 km in 55 minutes, which is 3,300 seconds. Pace is 3,300 / 10 = 330 seconds per km, or 05:30 /km. Speed is 10 / 3,300 × 3,600 = 10.91 km/h. At that pace a 5K takes 330 × 5 = 27:30, a half marathon takes 330 × 21.0975 = 1:56:02 and a marathon takes 330 × 42.195 = 3:52:04.

Try this example →

Common mistakes

  • Entering the distance in miles. The field is in kilometres, so a 6.2-mile run must be entered as about 10 km.
  • Putting the whole time in the minutes field with seconds as decimals (55.5). Enter 55 minutes and 30 seconds separately.
  • Treating the marathon projection as a prediction. It assumes an unchanged pace for the whole distance, which is rarely realistic.
  • Confusing pace with speed. Pace is time per km (lower is faster), speed is km per hour (higher is faster).

About this calculator

This calculator converts a distance and a finish time into your running pace per kilometer and your average speed in km/h, using the basic relationship between distance, time and speed. Beyond the raw pace figure, it projects that same pace onto standard race distances — 5K, 10K, half-marathon and marathon — so you can see what a training pace would translate to over a full race.

Runners use it both after a workout, to log how fast a given run actually was, and before a race, to plan a target pace that would produce a specific finish time. Coaches and running apps rely on the same math to build pacing strategies, since holding a steady pace per kilometer is usually more effective than running by feel alone, especially over longer distances where early over-pacing leads to a slower finish.

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Comments (1)

  • Editorial team

    The speed line is handy on a treadmill, which usually shows km/h: a pace of 5:00 per km is exactly 12 km/h. The race projections hold your pace constant, so treat them as a ceiling for a first attempt, not a plan; a sensible target for longer races is a little slower than the 5 km figure suggests. Distances are in kilometres only. Which race distance would you most like to see in the projection list?

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