Half Marathon Training Plan

It started, as most moderately poor decisions do, at parkrun. Someone mentioned they’d entered a half marathon. “It’s only 13.1 miles,” they said, cheerfully. You nodded. You went home, opened a browser, and suddenly you were knee-deep in spreadsheets, conflicting advice, and at least one forum thread suggesting you needed a heart rate monitor, a lactate test, and a sports scientist on retainer. You don’t. What you need is a sensible half marathon training plan, twelve weeks of commitment, and the occasional willingness to run in drizzle. Which, if you’re in the UK, is basically every week.

Half marathon entries in the UK jumped roughly 25% year-on-year according to recent entry data, and it’s easy to see why. The half is the sweet spot: long enough to feel like a proper achievement, short enough that you’re not rebuilding your entire life around Sunday long runs. If you’ve already got a 10K under your belt and you’re wondering what comes next, this is your answer.

Who Is This Half Marathon Training Plan For?

This plan is aimed at runners who can comfortably run 5K to 10K already. You don’t need to be fast. You don’t need a club vest. You do need to be able to get out three or four times a week, and you need to be honest with yourself about what “comfortable” actually means. If your 10K leaves you horizontal on the sofa for the rest of the day, give yourself another four weeks of base building first. No shame in it. Truly.

The plan runs over 12 weeks, with three to four runs per week. It’s built around three core principles used by coaches and club runners across the UK:

The majority of your running should feel easy (genuinely easy, not “I’m telling myself this is easy” easy)
One quality session per week: a tempo run, some intervals, or a progression run
A weekly long run that builds gradually and doesn’t leave you broken for the rest of the week

For a deeper look at what all those session types actually mean in practice, the types of running training guide over on The Easy Run is worth a read before you start.

The 12-Week Half Marathon Training Plan

Each week below lists four sessions. If life gets in the way and you can only do three, drop the midweek quality session before you drop the long run. The long run is the backbone of this plan. Everything else is scaffolding.

Weeks 1 to 3: Build the Base

Long run peaks at around 8 miles by the end of week three. Everything else is easy running with one short tempo effort per week (20 to 25 minutes at a comfortably hard effort, the kind of pace where you could say a sentence but wouldn’t want to). Total weekly mileage sits around 18 to 22 miles. This feels modest. That is the point.

Monday: Rest or easy 30-minute jog
Tuesday: Easy 4 miles
Thursday: Tempo session (20-25 min effort sandwiched in an easy run)
Sunday: Long run (6 to 8 miles at easy, conversational pace)

Weeks 4 to 7: Build the Engine

This is where the plan earns its keep. Long runs push up to 10 to 11 miles. The quality session becomes slightly spicier: think 4 x 1-mile at half marathon goal pace, or a 30-minute threshold run. Your legs will start to notice. Your social life may also start to notice, which is one of the more realistic downsides of half marathon training nobody mentions in the race brochure.

Monday: Rest
Tuesday: Easy 5 miles
Wednesday: Quality session (intervals or tempo, 45-50 min total)
Thursday: Easy 4 miles recovery
Sunday: Long run (9 to 11 miles)

Weeks 8 to 10: Peak Training

The long run hits its peak: 12 miles in week nine or ten, depending on how you’re feeling. If that sounds like a lot, it is, a bit. But arriving at the start line having run 12 miles in training means 13.1 on race day feels like a confident step forward rather than a leap into the unknown. Keep the easy runs genuinely easy. Garmin’s heart rate zone guide is useful here if you want to make sure your easy days are actually easy and not just “medium while lying to yourself.”

Weeks 11 to 12: Taper

You reduce mileage by around 30 to 40% in week eleven, and then again in week twelve. Keep the quality sessions in but shorter. The long run in week eleven caps at about 8 to 9 miles. In week twelve, 5 to 6 miles, nothing heroic. Your legs will feel fresh and slightly strange. You may feel an irrational urge to do more. Resist it with every fibre of your being. The hay is in the barn. Leave it there.

Half Marathon Pace: What Should You Actually Be Running?

This is the question everyone has and nobody wants to answer because the honest response is “it depends.” But here’s a practical starting point: if you have a recent 10K time, double it and add 10 to 15 minutes. That’s a rough half marathon finish estimate. From there, you can work backwards to a per-mile or per-kilometre target pace. Athletics Weekly has solid pace calculators if you’d prefer something more precise.

For context, the average UK half marathon finish time sits somewhere around 2:04 to 2:10 for men and 2:20 to 2:30 for women across mass-participation events, though the spread is enormous. Sub-2:00 is a goal worth chasing for many club runners. Just don’t set off at sub-2:00 pace in the first mile and then spend the next twelve miles paying for it. Every race report ever written contains some version of this mistake.

The Bits Nobody Tells You About Training for a Half

Here is some actual useful information that tends to get buried under the motivational quotes:

Shoes matter more over longer distances. If your current trainers are over 500 miles old or causing any niggles on your 10K runs, they will not improve at 11 miles. Now is a reasonable time to sort this out.
You will need to fuel on long runs over 75 minutes. A gel, some chews, a banana wrapped in cling film if you want to look properly committed. Practice this in training, not on race day.
One long run per week is enough. You don’t need two. You’re not an elite. Two long runs per week for an amateur runner is a fast track to injury, not improvement.
Sleep is a training session. Not in a cheesy way. Actually, in a physiological adaptation way. If you’re cutting sleep to fit in extra runs, you are going backwards.
Easy really does mean easy. If you can’t hold a conversation, you’re running too hard. The NHS physical activity guidelines describe this as “moderate intensity” for a reason.

If you’ve come straight from Couch to 5K and you’re wondering whether this is even a sensible next step, the post-Couch to 5K guide on this site maps out a more gradual route from 5K to 10K before you tackle the half marathon. Genuinely worth a look if you’re still fairly new to all this.

Race Day: Keep It Simple

Nothing new on race day. Not the shoes, not the gel brand, not the pre-race breakfast. Wear what you’ve trained in. Eat what you’ve tested. Start slower than you think you should. The second half of a half marathon will find you out if you’ve been optimistic in the first mile. Negative splits are not just something fast people do; they’re what you get when you manage your own enthusiasm early on.

The weather in the UK being what it is, assume it will be 12 degrees and sideways rain and dress accordingly. If it turns out to be 18 degrees and sunny, that’s a bonus. If you’ve dressed for 18 degrees and it’s 9 degrees with a headwind, race day becomes a much longer morning than you planned.

Real Talk

This 12-week half marathon training plan is a solid, no-nonsense framework for runners who already have some base fitness and want a clear structure without spending money on a coach or decoding an overly complicated spreadsheet. It works. Most 10K runners who follow it consistently will finish their half marathon feeling controlled rather than destroyed.

Best for: Runners with a recent 10K time who can train three to four days a week and have twelve weeks available before their race.

Not ideal for: Complete beginners (build your 5K base first), runners carrying an injury (see a physio before you start), or anyone who can only reliably train twice a week (the plan will feel too stretched to be effective).

12 weeks, three to four sessions per week
Long run is the priority: don’t skip it, don’t rush it
Easy runs should be genuinely easy, not medium
One quality session per week is enough
Taper properly or you’ll arrive at the start line tired
Nothing new on race day, ever

If you want to understand what your training sessions are actually doing to your body, the types of running training guide is a genuinely useful companion to this plan. Go read it, then lace up.

Half Marathon Training Plan for UK Runners: 12 Weeks, No Faff