Health tool
Running pace calculator & split chart
Fill in any two of distance, finish time and pace — the third is solved for you, along with average speed and a split chart you can copy, print or save as a PNG. Works in kilometres or miles.
Your target
Distance
Finish time
Pace
Splits
Uniform pace: the same pace is assumed for the whole distance; the last row is the finish line.
How it is calculated
Pace = finish time ÷ distance, so a 42.195 km marathon in 4:00:00 works out to about 5:41 per kilometre (9:09 per mile). Time = pace × distance, and distance = time ÷ pace. The tool converts with 1 mile = 1.609344 km and counts in seconds internally, so the last split total always lands exactly on your target time.
The split chart assumes you hold one steady pace from start to finish. Real races are rarely that tidy — hills, weather and fatigue all shift the middle kilometres — so treat the table as a pacing reference, not a prediction.
Common goals
Tap a row to load it into the calculator:
Calculate a symmetric barbell load from your plate inventory →
Method and sources
- Method / source
- Uniform-pace model: pace = finish time ÷ distance; time = pace × distance; distance = time ÷ pace. Conversion uses 1 mile = 1.609344 km; the half and full marathon presets use the World Athletics standard distances of 21.0975 km and 42.195 km. All math runs in seconds and only the display is rounded, so the last split equals the goal time exactly.
- Who it suits
- Runners who want a per-km or per-mile pace for a goal finish time, or a finish time / distance worked backwards.
- Who it does not suit
- Anyone needing a pacing plan that accounts for hills, heart-rate zones or fade; this tool makes no performance prediction or training prescription.
- Limitations
- The even-pace assumption ignores course profile, weather, fuelling and fatigue — the chart is a reference, not a race prediction or medical advice.
- Explanation updated
- Explanation updated: 2026-11-11 (not clinically reviewed)
Primary sources: World Athletics: marathon (42.195 km) · World Athletics: half marathon (21.0975 km)
Frequently asked questions
How is pace calculated?
Pace = finish time ÷ distance. A 42.195 km marathon in 4:00:00 works out to about 5:41 per kilometre. You can also solve backwards — pace and distance give the finish time, time and pace give the distance. Pick what to solve for at the top of the page.
Why are the half and full marathon 21.0975 and 42.195 km?
Those are the standard race distances set by World Athletics: 21.0975 km for the half marathon and 42.195 km for the marathon. The preset buttons use these exact figures, not approximations.
How do kilometres and miles convert?
1 mile = 1.609344 km. Miles you enter are converted exactly before computing; min/km and min/mile paces convert with the same constant (6:00/km ≈ 9:39/mile). The split chart can switch to one-mile rows.
Why does the last split land exactly on my target time?
The tool counts in seconds internally and only rounds for display; the final row renders the exact distance × pace value, so the cumulative total equals your goal time with no drift from per-row rounding.
Can this chart predict my race performance?
No. It only answers 'how fast per kilometre do I need to run to finish in X' — a uniform-pace model with no hills, weather, fuelling or fatigue. Real races are rarely even, so treat it as a pacing reference, not a prediction.
Where is my input stored?
Only in this device's browser storage, to refill the form next time. Nothing is uploaded; clearing browser data removes it.