A half marathon training plan built from your 5K
Sixteen weeks, four days a week, and a long run that climbs at a rate your legs can keep. The paces come from your current 5K; the goal time is scored for likelihood from the first week to the last.
Half marathon · 16 weeks
4 runs a week
Long run climbs to 17.7 km · the plan's own projection for this runner is 2:04:12
Who it is for
A runner who can comfortably run 10 km or more and has a recent 5K. The sample is a 27-minute parkrunner running 30 km a week who wants to go under two hours; the plan says honestly whether that target is in reach.
How the block is shaped
Base weeks establish easy pace and start the long run climbing by time on feet. The build adds a threshold session and a weekly speed session, with a cutback week every few weeks so the body absorbs the work. The peak puts goal pace inside the long run. A two-week taper keeps the sharpness and drops the load.
This is the plan the app builds for a 27:00 parkrunner running four days and about 30 km a week, with a longest comfortable run of 17 km. Your own block keeps the same shape; every distance and pace in it is priced from your times, not this runner's.
| Weeks | Phase | Weekly km | Long run |
|---|---|---|---|
| Weeks 1–2 | Base | 30.5–31.8 | 15–15.3 km |
| Week 3 | Build | 32.4 | 15.5 km |
| Week 4 | Cutback | 25.9 | 10.8 km |
| Weeks 5–7 | Build | 34.1–36 | 15.8–16.4 km |
| Week 8 | Cutback | 28.8 | 11.5 km |
| Weeks 9–10 | Build | 37.2–38.3 | 16.6–16.9 km |
| Weeks 11–13 | Peak | 41.4–43.1 | 17.2–17.7 km |
| Weeks 14–15 | Taper | 22–31.1 | 6.2–9.6 km |
| Week 16 | Race week | Race | — |
A real week from the plan
Not an illustration: this is week 7 of 16, a build week of 36 km, exactly as the plan engine wrote it for the runner above, with the paces it set. The coach reads each session's purpose to you before you start it and calls the pace as you run.
| Day | Session | Distance | Pace | What it is for |
|---|---|---|---|---|
| Tuesday | INTERVALS | 6.1 km · 43 min | 5:18/km | 6 × 600m @ 5:18/km — 90s jog. |
| Thursday | AEROBIC | 6.1 km · 43 min | 7:33/km → 6:43/km | Progressive aerobic. Start at a comfortable easy pace and build effort steadily across the run to a brisk aerobic finish. Teaches pacing discipline and aerobic efficiency. Never push into tempo territory. |
| Saturday | AEROBIC | 7.4 km · 52 min | 7:03/km | Easy miles. Relaxed and rhythmic — finish feeling you could go again. Finish with 6 × 20s strides — fast and relaxed, not a sprint, with an easy jog between each. Form work, not fitness work. |
| Sunday | LONG RUN | 16.4 km · 115 min | 7:03/km | Aerobic endurance. Focus on efficient form and steady energy management. |
Where the paces come from
From the race time you give the app, through the Daniels & Gilbert VDOT model: easy, threshold and interval paces for your fitness, not a chart's. The same model runs on this site — the parkrun time calculator shows the three paces a plan would be built from, and the goal time calculator scores a target against the weeks you have.
What changes as you run
A faster 5K, 10K or half mid-plan moves every pace. The fortnightly consistency check scales the next two weeks to what you actually ran. A new personal best at the goal distance inside six months is trusted over any projection.
Common questions
How long should my longest run be before a half?
The plan's peak long run for the sample runner is shown on this page, and it is set by time on feet rather than a fixed distance, so a faster runner covers more and a slower runner less. It passes well beyond the point where the race distance is a surprise without reaching it in training.
Is sub-2 realistic for a 27-minute 5K runner?
The projection from a 27:00 5K lands a little over two hours, which is why the sample plan's predicted time sits where it does. The goal time calculator on this site scores that gap against the weeks available; the app does the same every week and says so plainly.
What does a cutback week look like?
The same sessions at roughly three-quarters of the load, including a shorter long run. It is scheduled, not a reward for feeling tired, and it is the week the previous three are absorbed.
Can I start with less than sixteen weeks?
Yes, if your longest comfortable run is already near the plan's early long runs. The goal time calculator works out the minimum block from that distance; below it, the long-run climb becomes the injury risk the plan exists to avoid.
parkrun® is a registered trade mark of parkrun Limited. Outrunr is not affiliated with or endorsed by parkrun. VDOT is a trade mark of its owner. Outrunr implements the published Daniels & Gilbert formula and is not affiliated with them.