What you can solve here
Three modes, one calculator.
Pace mode is the most common: you ran a known distance in a known time, what was your average pace per kilometer or per mile? Plug in the numbers, get the answer in M:SS format.
Time mode projects forward: if you can hold this pace, what’s your finish time over a target distance? Useful for setting realistic race goals or estimating long-run finish times.
Distance mode runs the math the other direction: you ran for X minutes at Y pace, how far did you actually go? Helpful when your watch dies mid-run or when you want to plan a route by duration instead of distance.
Time inputs accept HH:MM:SS, MM:SS, or pure seconds. Pace inputs use M:SS per unit. Toggle units between kilometers and miles, the calculator converts internally and reports back in whichever you picked.
How the math works
Pace is just time divided by distance, normalized per unit. A 50-minute 10K is 50 minutes ÷ 10 kilometers = 5:00/km. The math is trivial; the value is the format. Splitting hours into minutes and seconds is what makes pace human-readable.
Speed (in km/h or mph) is the same data presented differently. A 5:00/km pace is 12.0 km/h. Speed sits on the result panel because some training plans and running watches express targets that way.
Conversion between miles and kilometers uses the exact factor: 1 mile = 1.609344 km. Many calculators round to 1.609 and accumulate a small error over the marathon distance. This one keeps the precise factor so a 26.2-mile marathon comes out to 42.195 km exactly.
Race-pace targets people commonly punch in
For reference, here’s what well-known finish times work out to in pace:
- Sub-25 minute 5K: 5:00/km (8:03/mi), competitive recreational runner
- Sub-50 minute 10K: 5:00/km, same pace held twice as long, harder than it sounds
- Sub-2-hour half marathon: 5:41/km (9:09/mi), a common goal for first-time half marathoners
- Sub-4-hour marathon: 5:41/km (9:09/mi), the same pace as the sub-2 half, held twice as long
- Sub-3:30 marathon: 4:58/km (8:00/mi), Boston-qualifying for many age groups
- Sub-3 marathon: 4:15/km (6:51/mi), serious recreational runner territory
Race pace and training pace should differ. Easy runs typically sit 60-90 seconds per kilometer slower than your race goal pace; tempo runs are 15-30 seconds slower; intervals are faster.
Why pace matters more than total time
Pacing is what keeps you from blowing up at kilometer 25 of a marathon. Running a 5:30/km first half and a 7:00/km second half gives the same average pace as running a steady 6:15/km the whole way, but the experience is night and day. Even pacing, or a slight negative split (faster second half), is the strategy that actually delivers PRs.
The pace calculator pairs naturally with a watch that gives live pace updates. Set your target pace before the race, then check your watch every kilometer to make sure you’re holding it. Going too fast in the first 5K is the most common reason people miss their marathon time goal.
Frequently asked questions
What’s a “good” pace? Depends on the distance and your training history. A 5:00/km is impressive for a beginner running 1K, average for a recreational runner over 5K, and elite-level over a marathon. Compare to your previous PRs, not to strangers.
Why is my GPS pace different from this calculator? GPS pace is real-time and varies with terrain, GPS signal quality, and how aggressively your watch smooths the signal. This calculator gives the average pace over the entire distance, which is what shows up on your final race time.
How do I convert pace to speed? The result panel shows it. For a quick conversion: 60 ÷ pace-in-minutes-per-km = speed in km/h. So 5:00/km is 12.0 km/h.
What about cycling or swimming? The math is identical, but typical paces and distances are different. Cyclists usually report speed in km/h or mph rather than pace. Swimmers usually use seconds per 100m. The calculator handles the underlying numbers either way, just enter the right units.