Five minutes saved over 10 kilometers is 30 seconds per kilometer. The course length is fixed, so the gap does not depend on how fast you already are.
5 × 60 seconds ÷ 10 km = 30 seconds per km.
In miles, a 10K is 6.214 miles. 300 seconds ÷ 6.214 = about 48 seconds per mile.
Three examples
| Current 10K | New 10K | Current pace | New pace |
|---|---|---|---|
| 60:00 | 55:00 | 6:00/km (9:39/mi) | 5:30/km (8:51/mi) |
| 55:00 | 50:00 | 5:30/km (8:51/mi) | 5:00/km (8:03/mi) |
| 50:00 | 45:00 | 5:00/km (8:03/mi) | 4:30/km (7:15/mi) |
Each row is the same 0:30/km change. The effort is not the same. Going from 6:00 to 5:30 and going from 5:00 to 4:30 are both 30 seconds per kilometer, and the second one is a much larger fitness jump.
The halfway check
Half of a 5:00 improvement is 2:30 at 5 km.
- A 55:00 goal should be near 27:30 at 5 km, not 25:00.
- A 50:00 goal should be near 25:00 at 5 km.
A faster first half means the second half has to be slower to land on the new clock, or you are headed for a bigger improvement than five minutes. The 10K pace calculator lists every kilometer for the target time.
What this does not tell you
The table is the pace the new clock requires. It is not a training plan, and it does not say the change is available in a given number of weeks. If you have a recent 5K, the race time predictor is the better check on whether 50:00 is close to current fitness. A 25:00 5K usually projects a 10K nearer 52 minutes than 50.
How long a 10K takes is the full even-pace chart. How to calculate running pace is the same division for any other gap you want to test. Speed for these paces is on the running speed calculator: 5:30/km is 10.9 km/h, and 5:00/km is 12.0 km/h.