Half Marathon Pace Calculator
Calculate half marathon pace, finish time, speed, mile splits, kilometre splits and a simple run-walk adjustment.
Enter A Target Or Pace
Pace Result
Pace needed for a 2:00:00 half marathon.
Half Marathon Distance And Pace
The recognised half marathon distance is 21.0975 km, which is about 13.1094 miles. Pace is the time taken for one kilometre or one mile. A 2-hour half marathon needs about 5:41 per km or 9:09 per mile. A 1:45 finish needs about 4:59 per km, while a 2:30 finish needs about 7:07 per km. The calculator can work from finish time to pace, or from pace to finish time. It also shows speed because some treadmills and training watches use km/h rather than pace.
Formula Method
Total seconds = hours x 3600 + minutes x 60 + secondsPace seconds per km = total seconds / 21.0975Pace seconds per mile = total seconds / 13.1094Speed km/h = 21.0975 / total hoursSplit time = pace seconds per km x split kilometresRun-walk finish time = running pace time + walk seconds per km x kilometresThe run-walk field adds a planned walking allowance to each kilometre. It does not adjust the running pace automatically for effort or recovery. For example, a runner who covers the running parts at 6:00 per km and walks 20 seconds every kilometre has an average pace of about 6:20 per km. That can be a useful way to plan a first race, but the break pattern should be tested in training. If a race has mile markers rather than kilometre markers, use the mile pace and mile split table for easier checking.
Common Half Marathon Pace Table
| Finish Time | Pace Per km | Pace Per Mile | 5 km Split |
|---|---|---|---|
| 1:20:00 | 3:48 | 6:06 | 18:58 |
| 1:30:00 | 4:16 | 6:52 | 21:20 |
| 1:40:00 | 4:44 | 7:38 | 23:42 |
| 1:45:00 | 4:59 | 8:01 | 24:53 |
| 1:50:00 | 5:13 | 8:24 | 26:04 |
| 2:00:00 | 5:41 | 9:09 | 28:26 |
| 2:10:00 | 6:10 | 9:55 | 30:49 |
| 2:15:00 | 6:24 | 10:18 | 32:00 |
| 2:30:00 | 7:07 | 11:27 | 35:33 |
| 3:00:00 | 8:32 | 13:44 | 42:39 |
Split Planning For Race Day
Even splits are easy to calculate but not always easy to run. A busy start can make the first kilometre slow. A downhill opening mile can make the pace look too fast. GPS watches can also drift on courses with trees, tunnels, sharp turns or tall buildings. Use official distance markers where available and check average pace rather than reacting to every small watch change. For many runners, the most useful plan is a controlled first 5 km, steady middle 10 km and a decision point near 16 km. If the target pace is already hard at 8 km, slow slightly before the final third becomes a struggle.
Treadmill, Watch And Marker Checks
Treadmills often ask for speed rather than pace, so the km/h result can help with controlled training. A treadmill set to 10.5 km/h is close to 5:43 per km, which is near 2-hour half marathon pace. Outdoor running adds wind, turns, surfaces and small hills, so do not assume a treadmill pace will transfer perfectly to race day. If you train by heart rate or effort, use the pace result as a reference rather than a command.
For watch setup, choose lap alerts that match the course markers. If the race has mile markers, mile laps reduce mental maths. If it has kilometre markers, kilometre laps give more frequent checks. Some runners also set a manual lap at each official marker, because GPS auto-lap can trigger early or late. A written pace band, pinned or saved on a watch, can be easier than calculating splits when tired.
Training And Safety Boundaries
This calculator does not judge whether a target time is safe or realistic. A half marathon is a long effort and training history matters. Increase distance gradually, practise fuelling, test shoes and clothing, and pay attention to heat, cold, injury signs and medical conditions. Anyone with chest pain, faintness, severe breathlessness, known heart concerns, recent illness or a medical condition should seek suitable medical advice before racing hard. The pace figure is arithmetic. Your body, training and race conditions decide whether it is sensible.
Worked Pace Example
Suppose a runner wants to finish in 1:55:00. That is 6,900 seconds. Dividing by 21.0975 km gives 327 seconds per kilometre, or 5:27 per km. Dividing by 13.1094 miles gives about 526 seconds per mile, or 8:46 per mile. A 5 km split would be about 27:16, a 10 km split about 54:31, and a 20 km split about 1:49:02. The final 1.0975 km then brings the finish to 1:55:00. If the runner adds 10 seconds of walking each kilometre, the average pace becomes slower unless the running sections are faster.
FAQs
What pace is needed for a 2-hour half marathon?
A 2-hour half marathon requires about 5:41 per km or 9:09 per mile over the official 21.0975 km distance.
How long is a half marathon?
The recognised distance is 21.0975 km, or about 13.1094 miles. Some watches may show slightly more because of GPS line and course positioning.
Should I pace by kilometres or miles?
Use the unit that matches your watch, course markers and habit. UK races may show mile markers, kilometre markers or both.
Does the run-walk field change running speed?
No. It adds planned walking seconds to the average. If you want the same finish time with walks, the running sections need to be faster.
Why does my GPS distance differ from the official distance?
GPS tracks your path and can drift. The official course is measured by approved methods, while a runner may weave, take corners wide or lose signal.
Can this set my race goal?
No. It converts time and pace. Use training results, recent races, health status and coaching advice when choosing a goal.
Sources
- World Athletics. (n.d.). Competition and technical rules. World Athletics. https://worldathletics.org/about-iaaf/documents/book-of-rules
- NHS. (n.d.). Physical activity guidelines for adults aged 19 to 64. NHS. https://www.nhs.uk/live-well/exercise/
- England Athletics. (n.d.). Running and road running guidance. England Athletics. https://www.englandathletics.org/