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What The Running Pace Calculator Works Out
- Pace per km: finishing time divided by distance. A 25-minute 5K is 5:00 per km. Common benchmarks: a 30-minute 5K (6:00/km) is a solid recreational milestone, 25 minutes a regular runner's target and 20 minutes (4:00/km) club standard. Parkrun's 5K format is the natural UK testing ground.
- Pace per mile: the same pace in the unit older race plans and many watches use; multiply per-km pace by 1.609 to get per-mile, so 5:00/km is about 8:03/mile.
- Speed: distance divided by time in km/h. 5:00/km is 12 km/h.
- Equal-pace table: deliberately naive projections of what your pace gives over 1 km to the marathon if you could hold it, which nobody does. Nobody holds their 5K pace for a marathon, and the gap between naive and realistic widens with distance, which is precisely why marathon pacing discipline matters.
- Target pace instead of time (advanced): enter a pace per km or per mile and the calculator works the other way, giving the finish time for the chosen distance, handy for setting a goal.
- Treadmill speed and track laps (advanced): the pace in mph for UK treadmills that display imperial, plus the 400 m and 200 m lap times to hit on a track.
- Easy run pace (advanced): most training plans anchor sessions to current race pace, with easy runs a minute or more per km slower and intervals faster. The card shows race pace plus 60 to 90 seconds per km.
- Realistic race predictions (advanced): Riegel's formula multiplies your time by the distance ratio to the power 1.06, which puts a 25-minute 5K runner around 52 minutes for 10K and roughly 4 hours for a marathon with appropriate training, rather than the 3:31 the flat projection suggests. Raise the exponent (1.08 to 1.10) if you fade over distance, lower it towards 1.04 if you are endurance-trained.
- Split table and negative split (advanced): a cumulative split sheet every kilometre or mile for the chosen distance. Add a negative split percentage to run the first half that much slower and the second half faster for the same finish time; 2% to 4% is typical for a well-paced marathon. Going off at half-marathon pace is the classic way to walk the last 10K.
Source and further reading: NHS: Couch to 5K.