Training plans · Half marathon
12-week half marathon training plan
Twelve weeks is the standard half marathon block. It is enough to stretch your long run to 18 km and sharpen your threshold, without the commitment of a marathon. This sample is set for a runner with a 50-minute 10K aiming at 1:50.
The plan at a glance
Daniels-style: VDOT-paced quality sessions (E/M/T/I/R) by phase. 16 quality sessions in total, with every fourth week lighter and a taper into race day.
Week by week
| Week | Phase | km | Key sessions | Long run |
|---|---|---|---|---|
| 1 | base | 30 | Threshold run 3.6 km | 8.1 km |
| 2 | base | 32 | Threshold run 3.8 km | 8.9 km |
| 3 | base | 35 | Threshold run 4.2 km | 10.2 km |
| 4 | base | 30 | Threshold run 3.6 km | 8.1 km |
| 5 | build | 39 | Threshold run 4.7 km, Intervals 4.7 km | 12 km |
| 6 | build | 42 | Threshold run 5 km, Intervals 5 km | 13.5 km |
| 7 | build | 44 | Threshold run 5.3 km, Intervals 5.3 km | 14.4 km |
| 8 | build | 37 | Threshold run 4.4 km, Intervals 4.4 km | 11.1 km |
| 9 | peak | 49 | Goal-pace run 5.9 km, Intervals 5.9 km | 17 km |
| 10 | peak | 51 | Goal-pace run 6.1 km, Intervals 6.1 km | 18 km |
| 11 | taper | 38 | Easy running | 11.6 km |
| 12 | taper | 20 | Easy running | Race day |
Training paces
Set from a recent 10k result, not the goal. Enter your own in the generator and they update.
- Easy6:16/km
- Marathon5:27/km
- Threshold5:06/km
- Interval4:39/km
- Repetition4:28/km
- Goal race5:13/km
Why threshold matters most for the half
A half marathon is raced just below your lactate threshold, the pace you could hold for about an hour. Raise that pace and your half marathon speed rises with it. That is why the threshold run anchors the plan.
Intervals at 5K effort join in the build phase to lift your top end. Goal-pace work in the peak phase teaches you to lock into race rhythm.
How the weeks build
Weeks 1 to 4 run 30, 32, 35 and 30 km, with one threshold run each. Weeks 5 to 8 run 39, 42, 44 and 37 km, and add intervals. Weeks 9 and 10 are the peak, at 49 and 51 km.
Every fourth week is lighter by design. The long run follows the same pattern: 8 km in week 1, 14 km by week 7, 18 km in week 10.
Week 10, the hardest week
Week 10 peaks at 51 km. Monday is rest. Tuesday, Thursday and Saturday are easy runs of about 7 km at 6:16/km.
Wednesday is a 6 km goal-pace run at 5:13/km. Friday is 6 km of intervals, with the fast repeats at about 4:39/km. Sunday is the 18 km long run, at easy pace.
Week 11 then drops to 38 km with no hard sessions. Race week is 20 km including the half.
Picking a goal you can hold
A 50-minute 10K predicts a half marathon of about 1:50, so this sample’s goal sits right on the prediction. That makes 5:13/km a pace you should be able to hold, not a hope.
Got a 52-minute 10K? The prediction moves to about 1:55. Enter it, and the generator sets the plan around that instead.
Missed a week?
In a 12-week plan, one lost week is fine. Skip it, don’t squeeze it in later. If you were ill, come back with a few easy days before the next quality session. If you lose two weeks or more, move the race goal back by a few minutes rather than rushing the long run.
A good first step towards a marathon
A half marathon block builds the habits a marathon needs: a weekly long run, structured quality days and a taper. Many runners use a spring half as a stepping stone to an autumn marathon.
Frequently asked questions
Is 12 weeks enough for a half marathon?
For a runner who can already run 8–10 km comfortably, yes. Beginners starting from a lower base may prefer the beginner plan below or a 14–16-week window.
How long should my longest run be?
Most half marathon plans peak at 18–21 km. This sample peaks at 18 km in week 10, two weeks before race day.
What 10K time predicts a 1:50 half marathon?
About 50 minutes. Use the race time predictor to convert any recent result.
Can I race a 10K during the plan?
Yes, in week 4 or week 8, the lighter weeks. Swap it for that week’s threshold run and keep the long run easy the next day. A faster time is worth entering in the generator, since it sharpens your paces.