How running pace is calculated
Pace, time, and distance are all tied together by one relationship, and this calculator can solve for whichever one you don't have:
Pace = Time ÷ Distance
Time = Pace × Distance
Distance = Time ÷ Pace
Worked example: you run a 5K (5 km) in 25 minutes. Pace = 25:00 ÷ 5 = 5:00 per km. To see that in miles, convert the pace by multiplying the seconds by 1.609344 (or just divide the same 25 minutes by 5 km converted to 3.107 miles): 25:00 ÷ 3.107 ≈ 8:03 per mile. Both describe the exact same effort — this calculator shows both automatically so you never have to convert by hand.
Once it has your pace, the calculator also works out your speed in miles per hour and km per hour (speed is just 60 divided by your pace in minutes), and — when you're solving for pace — how long that same pace would take you to finish a 5K, 10K, half marathon, or full marathon.
Common race pace chart
These are the paces needed to hit some popular goal times. Use them as a quick reference, or plug your own goal time into the calculator above for an exact split.
| Race | Goal time | Pace per mile | Pace per km |
|---|---|---|---|
| 5K | 20:00 | 6:26 | 4:00 |
| 5K | 25:00 | 8:03 | 5:00 |
| 5K | 30:00 | 9:39 | 6:00 |
| 10K | 45:00 | 7:15 | 4:30 |
| 10K | 50:00 | 8:03 | 5:00 |
| 10K | 1:00:00 | 9:39 | 6:00 |
| Half marathon | 1:45:00 | 8:01 | 4:59 |
| Half marathon | 2:00:00 | 9:09 | 5:41 |
| Half marathon | 2:15:00 | 10:18 | 6:24 |
| Marathon | 3:30:00 | 8:01 | 4:59 |
| Marathon | 4:00:00 | 9:09 | 5:41 |
| Marathon | 4:30:00 | 10:18 | 6:24 |
Notice that a half marathon and a marathon at exactly double the time (1:45:00 vs. 3:30:00, for example) share the same pace — that makes sense, since the marathon is exactly double the distance of the half.
Why race predictions from one pace are optimistic
It's tempting to take your 5K pace and multiply it out to predict a marathon time, but that almost always produces a number that's faster than what you'll actually run. Holding an identical pace gets harder, not easier, as distance increases: glycogen stores run low, muscles fatigue, and heat and hydration become bigger factors the longer you're out there.
Most runners naturally slow down somewhat over longer distances — the gap between 5K pace and marathon pace is typically much larger than the gap between marathon pace and half-marathon pace. So treat any equal-pace projection (including the finish-time table this calculator shows in Pace mode) as a best case, achievable with strong endurance training and good pacing, not a guarantee. It's a useful ceiling to aim for, not a floor.
Pacing tips for a negative split
A negative split means running the second half of a race faster than the first — a strategy strongly associated with strong finishes and personal bests, because it works with fatigue instead of against it. In practice: start 5 to 10 seconds per mile slower than your goal pace for the first third of the race, settle into goal pace through the middle, and let yourself pick it up in the final third if you're feeling good. Starting even slightly too fast is one of the most common ways races go wrong, since the energy you burn in the first mile isn't available later when you need it most.