Half Marathon Pace Calculator
The Distance Where Pacing Discipline Actually Pays Off
At 21.0975 km, the half marathon sits in a demanding middle ground — too long to run on pure speed, too short to fall back on marathon-style conservative pacing. Runners who go out even slightly too aggressive over the first 5K often lose more time in the final 5K than they gained early, which is exactly why a checkpoint-based pacing plan is worth building before race day rather than during it.
The Formula
Both directions use the official half marathon distance:
Finish Time = Pace × Half Marathon Distance (21.0975 km / 13.1094 mi)
The result includes checkpoint splits at 5K, 10K, 15K, 20K, and the finish, each derived from applying the same per-kilometer or per-mile pace consistently across the full distance.
Where This Calculation Matters
- Checkpoint pacing — comparing your actual 10K and 15K split against the plan catches an early pacing error while there's still time to correct it.
- Bridging 10K training into half marathon racing — runners moving up from shorter races often need a concrete pace adjustment, and this shows exactly what that adjustment looks like in split times.
- Negative-split strategy — some runners deliberately target a slightly slower first half and faster second half; having exact even-pace splits as a baseline makes that strategy easier to execute precisely.
- Race-day goal confirmation — checking that a target pace produces the finish time you're actually aiming for, before you're 10K into the race and realizing the math doesn't work.
Splits at an Even 4:30/km Pace
Computed directly from the formula above:
| Checkpoint | Split time |
|---|---|
| 5K | 22:30 |
| 10K | 45:00 |
| 15K | 1:07:30 |
| 20K | 1:30:00 |
| Finish (21.0975K) | 1:34:56 |
How to Use This Calculator
- Choose a mode — Goal Finish Time (find pace) or Goal Pace (find finish time).
- Select the pace unit — per km or per mile.
- For Goal Finish Time: enter Hours, Minutes, and Seconds.
- For Goal Pace: enter Minutes and Seconds per unit.
- Select Calculate to see the result along with checkpoint splits.
Related Calculations
For the full marathon distance version of this calculation, see the Marathon Pace Calculator. To check aerobic fitness relative to your target pace, check the VO2 Max Calculator.