Built by Tommo, Verus founder — free to use, no account required.
Half Marathon Training Duration Calculator
From a standing start to race-ready — the real timeline, not the generic one.
Half Marathon Training Duration Calculator
Pick where you're starting from, and see how many weeks the block actually takes — and, with a race date, the week to start.
Where you're starting from
Training block
12-16 weeks
Base
5 weeks
Raise weekly volume and consistency. No heroics — this is where most of the injury risk in the whole block gets managed.
Build
7 weeks
The longest sessions, threshold work, and race-pace effort layered into them.
Peak
2 weeks
The hardest stretch of the block — the volume and intensity both near their maximum.
Taper
2 weeks
Volume drops sharply, intensity mostly stays. This is where the training becomes fitness.
General planning guidance based on well-established, mainstream training-week ranges — not a personalised coaching plan. Uses the longer end of the range for the phase breakdown and start date, since starting a little early costs a taper week and starting a little late costs the race.
About This Tool
Most half marathon plans assume you're already covering 15-20 miles a week and can run a 10K — for that runner, 12-16 weeks is genuinely right. For anyone else, the real number is longer, and this calculator asks where you're starting from rather than assuming the fittest reasonable case.
How To Use It
- Pick the description that matches your current running.
- Add a race date if you have one, to get a start-by date.
- Read the weeks needed and the base/build/peak/taper breakdown.
- Use the Training Pace Calculator alongside it once you have a recent time, to get the actual paces the block should be run at.
Most half marathon plans assume the same runner: already covering 15-20 miles a week, able to run a 10K. For that runner, 12-16 weeks is genuinely right. For anyone building towards that starting point, the real number is longer, and the calculator above works from where you actually are rather than the fittest reasonable case.
The four starting points
| Where you are now | Weeks to the start line | What the time is for |
|---|---|---|
| Not currently running | 30-38 weeks | Six or so months building to a comfortable 10K and consistent weekly volume, then a 12-16 week half block on top. |
| Running 30 minutes comfortably | 17-26 weeks | Two to four months raising volume and the long run before the specific block begins. |
| Running 15-20 miles/week, can run a 10K | 12-16 weeks | The runner every published half marathon plan is written for. |
| Running 25+ miles/week with a recent 10K | 8-12 weeks | You already have the base — the block is about the long run and race-pace work. |
The session that actually decides it
A half marathon is close enough to raw endurance that the long run dominates the block more than any other session. It should reach 10-12 miles before race day, built up in small steps rather than jumped to — extending it too fast is the most common way a half marathon block ends early.
- Increase the long run gradually and take a lower-volume week roughly every fourth week.
- Most of your weekly mileage should be genuinely easy — slower than feels dignified. It's what lets the volume happen at all.
- One session a week at or near race pace teaches your legs what 13.1 miles at effort actually feels like, which the long run alone doesn't.
- Consistency over months beats intensity over weeks — four steady months gets you further than six brilliant ones and an injury.
What the weeks are actually for
Whatever total the calculator gives you, it breaks into the same four phases — base, build, peak, taper — in the same rough proportions a marathon block does, just compressed. The taper matters just as much at this distance: cutting it is a reliable way to arrive tired rather than sharp.
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Frequently Asked Questions
How long does it take to train for a half marathon?
12-16 weeks if you're already running 15-20 miles a week and can cover a 10K — that's the runner most published half marathon plans are written for. From a standing start, allow six to nine months: several months building a running habit and weekly volume, then the specific block on top.
Can a beginner run a half marathon in 12 weeks?
Only if 'beginner' means new to the half marathon distance specifically, not new to running. Someone who can already run 30 minutes comfortably can often get there in 17-26 weeks with a sensible build. Someone starting from zero needs closer to seven to nine months total.
How many miles a week for half marathon training?
Peak weeks in a half marathon block typically run 20-30 miles for a finish-focused plan, higher for a time goal. The long run is the session that matters most and should reach 10-12 miles before race day, built up gradually rather than all at once.
Is 8 weeks enough to train for a half marathon?
Only if you already have a running base and a recent shorter race behind you — eight weeks is a sharpening block, not a building one. From under 10 miles a week, eight weeks raises real injury risk because the schedule is compressing the part that has to happen slowly.
What pace should I run my half marathon training at?
Mostly easy — conversational pace, most weeks. The long run and any tempo work are where race-specific effort belongs. The Training Pace Calculator on this site turns a recent race result into the actual paces for each session type.