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CALCPARK

Pace Calculator

Running pace per km or mile from time and distance, finish time from a pace, or distance covered – with 5K, 10K, half and marathon presets, speed and even splits.

Calculated on your device
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How to use it

  1. Pick what to solve for: pace (from time and distance), finish time (from pace and distance) or distance (from time and pace).
  2. Choose kilometres or miles. Switching converts the distance and pace you already typed.
  3. Enter the distance – or tap a race preset – and the time or pace. The result updates as you type.
  4. Read the pace in both units, the speed in km/h and mph, the treadmill setting and the split table for every whole kilometre or mile.
  5. Copy the summary or the link; the link restores all inputs.

Example

A 10 km run finished in 50 minutes: 3,000 s ÷ 10 km = 300 s/km = 5:00 min/km. Per mile: 300 × 1.609344 = 482.8 s = 8:03 min/mi. Speed: 10 km ÷ (50 ÷ 60) h = 12.0 km/h (7.46 mph). Every kilometre split is 5:00 later than the last, so the 5 km mark passes at 25:00. To hold the same pace in a half marathon you would finish in 21.0975 × 300 s = 6,329 s = 1:45:29.

Formulas and assumptions

pace (s per km) = time (s) ÷ distance (km)
time (s) = pace (s per km) × distance (km)
distance (km) = time (s) ÷ pace (s per km)
pace per mile = pace per km × 1.609344
speed (km/h) = distance (km) ÷ time (h) = 3,600 ÷ pace (s per km)
speed (mph) = speed (km/h) ÷ 1.609344

Splits assume a perfectly even pace, which is the usual target for road races; real splits vary with terrain, wind and fatigue. Times are rounded to whole seconds after the calculation, so a displayed pace of 4:59 may correspond to 4:58.6. Race distances are the World Athletics standard distances; a GPS watch typically reads 1–2 % long on a certified course because it cannot follow the measured shortest line.

Treadmill note: Jones and Doust (1996) found that a 1 % gradient most accurately reflects the energetic cost of outdoor running at speeds between 2.92 and 5.0 m/s (about 5:42 to 3:20 min/km). At easy paces the difference is small enough to ignore.

Sources: World Athletics – Competition and Technical Rules (road race distances), Jones & Doust 1996, J Sports Sci – A 1% treadmill grade most accurately reflects the energetic cost of outdoor running, NIST – SI units and conversion factors (mile = 1,609.344 m).

Choosing a race pace

A common rule of thumb is that a well-trained runner slows by roughly 5–6 % per doubling of distance (Riegel’s endurance model uses the exponent 1.06): a 50:00 10K predicts about 1:50 for a half marathon and 3:50 for a marathon. Use the time mode to turn a target pace into a finish time, then the split table to check what the first few kilometres should look like.

Questions

How do I convert min/km to min/mile?
Multiply the pace by 1.609344. 5:00 min/km is 300 s × 1.609344 = 482.8 s, i.e. 8:03 min/mile. The calculator shows both units for every result.
What pace do I need for a 4-hour marathon?
4:00:00 is 14,400 s; divided by 42.195 km that is 341.3 s/km, i.e. 5:41 min/km or 9:09 min/mile. Enter the marathon preset and 4 h in pace mode to see it.
What speed should I set on the treadmill?
Speed in km/h is 60 ÷ pace in minutes: 5:00 min/km is 12.0 km/h, 6:00 min/km is 10.0 km/h. The tool shows the setting in km/h and mph and suggests a 1 % incline for an outdoor-equivalent effort.