How to Go From 10K to Half Marathon in Eight Weeks

Eight weeks, three runs a week, and a long run that climbs in low steps: the route to your first half marathon, starting from the 10K you already run.

• A plan built on three runs a week, plus an optional fourth easy one if you have the time and the legs.
• A long run that grows by about a mile at a time, topping out around 11 miles.
• How to set a cautious race pace from a recent 10K.
• The full eight-week schedule, with a cutback week in the middle and two lighter weeks at the end.
• What to do when you miss a workout, or a whole week.

If you run a 10K (6.2 miles) two or three times a week, you’re already halfway there, quite literally: your legs know the motion, and your breathing holds up for an hour without asking for a break. Getting to the 13.1 miles of your first half marathon takes eight weeks and a logic you’ll need some patience to respect. The long run grows like a staircase built one step at a time, and every step is low enough to climb without thinking about it.

Where You Start and Where You Finish

The starting point is the week you have now: three runs of around 6 miles, or two, with the occasional three-run week. The plan keeps that framework and changes what goes into it. Each run gets a specific job, and only one of the three gets longer. The fourth stays optional, and the schedule holds up without it.

The finish line, in training terms, is a long run of about 11 miles, run easy, two weeks before race day. You don’t need to cover 13.1 miles in training: the last two are carried by the fitness you build over six weeks and the freshness the final two weeks give back. Running them beforehand would mean standing at the start with that Sunday’s fatigue still in your legs, which is exactly what you want to avoid if you’re worried about going the distance.

The same principle keeps injuries away. Your body never takes a jump: the long run climbs by about a mile a week, total volume follows without sudden spikes, and after three weeks of building comes a lighter one. If you’ve already run a half and now want to run it faster, that’s a different kind of work, and you’ll find it in the plan to improve your half marathon time.

The Three Workouts of the Week

The long run is the heart of the plan, and you run it slow. Your guide is your breath: you should be able to talk in full sentences, without breaking them up to breathe, from the first mile to the last. That’s conversational pace. If halfway through you catch yourself grabbing air between words, slow down until the sentence comes back whole, even when your watch shows a pace that feels embarrassing. The long run trains duration, getting your legs and heart used to staying in motion for an hour and a half or more, and speed adds nothing here. The final miles feel like the first ones, with no closing surge to prove a point.

Midweek comes race pace, the workout that teaches you the speed you’ll hold in the half. To find it, take a 10K you’ve run in the last four to six weeks, in a race or a hard training run, work out your average pace per mile and add 30 to 50 seconds to it. If you ran a 55-minute 10K, about 8:50 per mile, you’ll train between 9:20 and 9:40. The estimate is cautious on purpose, because over eight weeks learning to hold a pace matters more than nailing it to the second: the right feel is an effort that lets you get out a short sentence and not much more. If you don’t have a recent 10K, a test over the distance will give you one in a single morning. Every session opens with about a mile easy and closes with half a mile easy, and between reps you jog slowly for three minutes, without stopping. If the pace already feels heavy halfway through the first rep, your reference was too optimistic: slow down by about 15 seconds per mile and stick with that number for the rest of the plan.

That leaves the easy runs, which look a lot like the ones you already do, with one difference: you run them at the same breathing as the long run, and they stay easy even on days when your legs feel great. Their job is to put miles into the week without adding fatigue, so that the long run and race pace find your legs ready. This is the workout people get wrong most often, out of too much zeal, and running it harder drains freshness from the next session without getting you anywhere sooner.

One layout that works: race pace on Tuesday, easy on Thursday, long run on Sunday. The fourth run, if you do it, goes on Friday, short and slow.

The Eight-Week Plan

The race pace column shows only the main part of the session: warm-up, recoveries and cool-down stay as described above.

Week four steps down on purpose. Three weeks of building leave a fatigue in your legs that you can’t see in any single workout but that adds up, and the fitness built over those days needs a few lighter ones to settle in. On the long-run staircase, this is the landing: a flat stretch halfway up, where your breathing gets back in order before the taller steps.

It’s also the week you’ll most want to skip, because your legs feel good and 7 miles seems like nothing. Run it as written anyway. Reach week five rested and you’ll handle the move up to 10 and then 11 miles; turn the cutback into another full week and that fatigue lands on you right there, on the two highest steps of the staircase.

In the last two weeks the long run drops to 8 miles and then gives way to the race, while race pace stays, only shorter: you cut volume and keep your body used to the speed. How you feel in those days can throw you. On the first runs of week seven your legs may feel heavy, then oddly restless, as if they had energy to burn and nowhere to spend it. You may also feel like you’re losing fitness, precisely because you’re training less, when in fact it’s the accumulated fatigue working its way out.

The plan holds if you add nothing during those fourteen days: no test long run, no extra run to reassure yourself. The fitness is already built, and what’s left is to show up rested.