Running Pace Calculator
Compute running pace, time, or distance — give any two and we compute the third.
Worked examples
10 km in 50:00. 3,000 seconds ÷ 10 km = 300 seconds per km, so your pace is 5:00/km (8:03/mi), a speed of 12.00 km/h.
Half marathon in 1:55:00. 6,900 seconds ÷ 21.0975 km ≈ 327 seconds per km, or 5:27/km (8:46/mi).
Marathon in 4:00:00. 14,400 seconds ÷ 42.195 km ≈ 341 seconds per km. You need 5:41/km, or 9:09/mi, from the first step to the finish.
Reading the split table
The splits hold one pace the whole way. Real races rarely work like that: hills, wind, heat and fatigue move them around. Use the table as a target and check your watch at each marker. If you are well ahead of the table early on, that is usually the moment to settle down rather than bank time you may have to pay back late.
Common mistakes
- Mixing units. Pace per km and pace per mile differ by a factor of 1.609. Check the unit toggle before comparing with a training plan.
- Putting minutes in the hours box. Hours, minutes and seconds have separate boxes: 50 minutes is 0 / 50 / 0.
- Trusting GPS on a track or treadmill. Track and treadmill distances are exact, while GPS can drift on short loops and shift your pace by a few percent.
How this is calculated
Pace = total time / distance.
Time = pace × distance.
Distance = total time / pace.
Speed = 3,600 / pace in seconds per unit. Other-unit pace converts with 1 mile = 1.609344 km.
Splits multiply your pace by each checkpoint distance (every km or mile up to 12, every 5 up to 60, every 10 beyond), so they assume an even pace.
Format is M:SS or H:MM:SS depending on duration.
Frequently asked questions
How do I convert pace from min/km to min/mile?
Multiply the pace in seconds per km by 1.609344 to get seconds per mile. A 5:00/km pace is about 8:03/mi, and the calculator shows the other unit for you.
What pace do I need to run a marathon in under 4 hours?
Four hours is 14,400 seconds over 42.195 km, which is about 341 seconds per km: 5:41/km or 9:09/mi, held from the start to the finish.
Do the split times account for hills or fatigue?
No. Each split is your pace multiplied by the distance, so it assumes a perfectly even effort. Use it as a target and expect real splits to move with terrain, wind and fatigue.