🏃♀️ Half Marathon Pace Calculator
Convert your 21.1 km race goal into per-kilometre and per-mile splits, ideal negative split strategies, and marathon projections.
Average pace
4:59 /km
8:01 /mi
Negative split pacing
Start at 4:56 /km then finish final 5K at 4:50 /km
Marathon projection
3:41:33
Assuming similar pacing and endurance
Kilometre Splits
| KM | Cumulative Time |
|---|---|
| 1 | 0:04:59 |
| 2 | 0:09:57 |
| 3 | 0:14:56 |
| 4 | 0:19:54 |
| 5 | 0:24:53 |
| 6 | 0:29:52 |
| 7 | 0:34:50 |
| 8 | 0:39:49 |
| 9 | 0:44:48 |
| 10 | 0:49:46 |
| 11 | 0:54:45 |
| 12 | 0:59:43 |
| 13 | 1:04:42 |
| 14 | 1:09:41 |
| 15 | 1:14:39 |
| 16 | 1:19:38 |
| 17 | 1:24:36 |
| 18 | 1:29:35 |
| 19 | 1:34:34 |
| 20 | 1:39:32 |
| 21 | 1:44:31 |
Mile Splits
| Mile | Cumulative Time |
|---|---|
| 1 | 0:08:01 |
| 2 | 0:16:01 |
| 3 | 0:24:02 |
| 4 | 0:32:02 |
| 5 | 0:40:03 |
| 6 | 0:48:03 |
| 7 | 0:56:04 |
| 8 | 1:04:05 |
| 9 | 1:12:05 |
| 10 | 1:20:06 |
| 11 | 1:28:06 |
| 12 | 1:36:07 |
| 13 | 1:44:07 |
How to Use This Calculator
Enter goal finish time
Use race goal or recent time trial for realistic outputs.
Review pace per km/mile
Use these numbers to set treadmill speeds or pace groups.
Adopt negative split strategy
Aim to run slightly slower for the first half, then pick up pace after 10–15 km.
Print splits for race day
Use kilometre and mile tables to stay on track throughout the course.
Formula
Pace per km = Finish Time ÷ 21.0975 • Pace per mile = Finish Time ÷ 13.1094
Splits multiply pace per unit by distance markers. Marathon projection approximates time by scaling half marathon pace with a fatigue factor (× 2.11).
Negative split pacing: start at 99% of average pace, finish final 5 km at 97% to account for fitness improvements and mental kick. Adjust percentages to suit training level.
Training Tips
Success in the half marathon hinges on tempo runs, threshold workouts, and long-run stamina. Use pace data to structure workouts leading up to race day.
Key workouts
- Tempo runs: 20–40 minutes at goal pace + 10 seconds per km.
- Long runs: build to 18–22 km with final 5 km at goal pace.
- Intervals: 4×2 km at goal pace with 2-minute jog recoveries.
Race day strategy
- Aim for even or negative splits using course markers.
- Hydrate according to plan (every 5 km) and fuel from 7–8 km onwards.
- Adjust pace for hills or weather; use perceived effort plus pace feedback.
Frequently Asked Questions
What is a good half marathon pace?
Recreational runners often target 5:00–6:30 min/km (8–10:30 min/mile). Sub-90 minutes is competitive amateur level.
How can I estimate marathon time?
Use the projection as a starting point, then adjust based on training history and endurance. Marathon pacing is typically 5–10% slower.
Should I account for course elevation?
Yes. Use hill-adjusted pace calculators or adjust splits manually for major climbs/descents.
Do I need to hit goal pace in training?
Practice segments at goal pace, but save full distance at goal pace for race day to avoid burnout.
How often should I update my goal?
Recalculate after tune-up races or every 6–8 weeks to reflect fitness gains.