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Pace, time, distance,
solve for any one.
A precise running-pace calculator. Enter any two of pace, time, or distance — get the third instantly, plus per-km and per-mile splits. Includes 5K, 10K, half-marathon, and marathon presets in metric or imperial.
Inputs
Solve for…
Time + distance → pace per km/mi.
- Distance
- 5 km
- Total time
- 25:00
- Pace
- 5:00/km · 8:03/mi
Pace
5 km · 5:00/km
≈ 8:03/mi
Splits
Per kilometer
| Mark | At | Cumulative |
|---|---|---|
| 1 | 1 km | 5:00 |
| 2 | 2 km | 10:00 |
| 3 | 3 km | 15:00 |
| 4 | 4 km | 20:00 |
| 5 | 5 km | 25:00 |
Field guide
How running pace is calculated.
Three numbers describe every run, and they're related by a single equation:
pace = time ÷ distance
distance = time ÷ pace
Given any two, the third falls out. The trick is keeping units consistent — most pace formulas are written for seconds and kilometers (or miles), so the calculator normalizes whatever you type into seconds-per-km internally and converts back at the boundary.
min/km vs min/mile
One mile is exactly 1.609344 kilometers, so a 5:00/km pace is an 8:03/mi pace. The conversion goes:
sec_per_km = sec_per_mi ÷ 1.609344
The hero number above shows whichever unit you're working in, and the composition row immediately below shows both — so you never have to hand-convert.
Common race distances
- 5K: 5 km / 3.107 mi
- 10K: 10 km / 6.214 mi
- Half marathon: 21.0975 km / 13.109 mi
- Marathon: 42.195 km / 26.219 mi
- 50K ultra: 50 km / 31.069 mi
- 100K ultra: 100 km / 62.137 mi
The four most common (5K, 10K, Half, Full) are wired into the calculator as one-tap presets.
What's a "good" pace?
Pace ranges vary widely with age, training, and event. Rough yardsticks for healthy adult runners on flat terrain:
- Casual jogger: 6:30–7:30 /km (10:30–12:00 /mi)
- Recreational runner: 5:30–6:30 /km (8:50–10:30 /mi)
- Trained amateur: 4:30–5:30 /km (7:15–8:50 /mi)
- Competitive amateur: under 4:00 /km (under 6:25 /mi) for shorter distances
- Elite: under 3:00 /km (under 4:50 /mi) at marathon distance and below
Don't take these as targets — they're snapshots of where different cohorts cluster, not advice. Improvement comes from consistency, not chasing a number.
The cardinal pacing mistake: starting too fast
Most amateur runners, especially in their first race — go out 30–60 seconds per kilometer faster than their goal pace in the opening 1–2 km, then pay heavily in the second half. The fix is the negative split: aim to run the second half of the race slightly faster than the first. For a 25-minute 5K target (5:00 /km), that means going through 2.5 km at maybe 5:05 /km and finishing at 4:55 /km. It feels conservative for the first kilometer; that's the point.
Even pace vs negative split vs positive split
- Even pace: every km at the same time. The classic textbook strategy and roughly what world records look like.
- Negative split: second half faster than first. Slightly easier to execute physiologically; almost all marathon PRs are negative-split.
- Positive split: second half slower than first. The default outcome for under-trained or over-eager runners.
Worked example
You want to break 25 minutes for a 5K. Time = 25:00, distance = 5 km, so pace = 25:00 ÷ 5 = 5:00 /km (8:03 /mi). Target splits are then 5:00 / 10:00 / 15:00 / 20:00 / 25:00. To negative-split, plan 5:05 / 10:05 / 15:00 / 19:55 / 24:55 — first half slightly slower, second half slightly faster, total still under 25.
What this calculator doesn't model
- Hills: steady-state pace assumes flat terrain; expect to add 8–15 seconds per km of net climb.
- Heat: every 5°C above 15°C costs roughly 1–2% of marathon time.
- Wind: a 10 mph headwind adds about
10 sec/km; a tailwind doesn't fully compensate. - Race effects: adrenaline, drafting, crowd, course turns. Expect a 1–3% boost over a tempo run of the same distance.
Disclaimer
This calculator is a planning tool, not a coach. Use the splits as targets and adjust based on terrain, conditions, and how the day actually feels.