How to prepare for a half marathon, from first week to race day.

How to prepare for a half marathon, in one paragraph

To prepare for a half marathon, give yourself 8 to 16 weeks depending on how much you run now. Run four or five days a week, mostly easy. Build the long run to 10 to 12 miles, add one faster workout a week, rehearse your race fuel, and taper for the last 10 to 14 days.

That is the whole job. The rest of this post is the detail: how to pick the length of your block, how far the long run needs to go, and what each week should look like. In more than ten years of coaching, the half marathoners who struggle rarely lacked a plan. They had the wrong length of plan for where they started, so they either rushed the build and got hurt or dragged it out and went stale.

How long to train for a half marathon

How long half marathon training should be depends on your current weekly mileage, not on the race. The 13.1 miles are the same for everyone. The distance between your normal week and a week that can carry you through them is not.

If you are starting from zero, the first few weeks of a running habit come before any of this. If the race is closer than the table allows, keep the date and change the goal: run it to finish and learn, then race the next one.

I am writing an 8-week and a 12-week half marathon plan to sit alongside this post. Until they are up, the structure below is enough to build your own.

Build the week before you build the long run

A half marathon is mostly an aerobic event. The fitness that carries you through mile 11 comes from the total running in your week far more than from any single session, so weekly volume is the first thing to grow.

• Four days a week is the floor, five is better. Three runs a week can get you to the finish, but the last three miles will be a negotiation.
• Add about 10% a week at most, and drop back by 15 to 20% every third or fourth week. The cutback week is where the previous three weeks turn into fitness.
• Run easy days easy. Conversational, slower than feels useful. Easy runs that drift too fast are the most common reason a half marathon block stalls in the middle.

For a first half, a peak of 20 to 30 miles a week is enough to finish well. Runners chasing a time usually peak between 30 and 45. More only helps if you can absorb it without sleep and soreness going the wrong way.

The longest run before a half marathon

For most runners, the longest run before a half marathon should be 10 to 12 miles. You do not need to cover 13.1 in training. Race day adrenaline, a taper and fresh legs carry you the last mile or two, and a training run that long costs more recovery than it returns for most first-timers.

Two adjustments:

• Cap the long run by time as well as distance. If 12 miles takes you well over two hours, stop around the two-hour mark. Past that point you are adding fatigue faster than fitness.
• Experienced runners can go longer. If you run 30+ miles a week and want a time, long runs of 13 to 15 miles build the durability that keeps your pace from sagging late.

Build the long run by a mile at a time, hold it flat every third week, and run your longest one two to three weeks before the race. How long your long run should be covers the reasoning in more depth.

One workout a week does the rest

Once the week is stable, add one quality session. For the half, threshold work does most of the lifting, because race pace sits close to your threshold. A progression that works:

1. Weeks 1 to 3: 4 to 6 x 3 minutes at comfortably hard, 90 seconds easy jog between.
2. Weeks 4 to 7: 3 x 1 mile at tempo pace, 2 minutes easy between.
3. Weeks 8 onward: 4 to 6 miles continuous at goal half marathon pace, folded into the middle of a longer run.

Add 4 to 6 short strides after two of your easy runs each week. They take five minutes and keep your stride from flattening out under all the steady mileage.

To set goal pace, start from a recent 5K or 10K rather than a hope. The half marathon pace chart gives the splits for every finish time from 1:20 to 2:30, and sub-2 hour pace has its own breakdown if that is your line.

Rehearse fuel and kit on long runs

Most half marathons take between 1:30 and 2:45. Under about 75 minutes you can get by on breakfast. Past that, take a gel or chew around 45 minutes and every 30 to 40 minutes after, and practice it on long runs so your stomach knows the routine.

Do the same with everything else you will race in: shoes with 30 to 60 miles on them, the exact shorts and socks, the same breakfast at the same hour before. What to eat before a half marathon lays out the race-morning meal.

When a week goes sideways

Every block has one. A cold, a work trip, a week where the long run did not happen. How you handle it matters more than the week itself, because the instinct is to make up the missed miles, and that is the move that turns one lost week into three.

• Missed a few days: pick the plan back up where it is. Do not double up.
• Missed a full week: repeat the last week you completed, then carry on. The block gets one week shorter at the end, which is fine.
• Sick with a fever or anything below the neck: no running until it clears, then two or three easy days before the next workout.
• Missed two weeks or more inside the last month: keep the race, lower the goal. Running it as a long run with a few miles at pace is a better day than forcing a time your training no longer supports.

Pain that changes how you run is different from a missed week. Stop, and use a return to running program rather than the training plan to come back.

Taper for 10 to 14 days

The half needs a shorter taper than the marathon. Two weeks out, drop weekly volume by about a quarter. In race week, drop it by about half. Keep a little pace in both weeks, such as 3 x 1 mile at goal pace the first week and a few strides before the race, so your legs remember what race effort feels like.

The pattern I watch for most in race week is the fitness test. A runner feels flat after a few lighter days, panics, and runs a hard session to check. There is no workout in the last week that makes you faster on Sunday, and there are several that make you slower.

Race day: the first three miles decide the last three

Start 5 to 10 seconds per mile slower than goal pace for the first two or three miles. Settle onto pace through the middle. If you still feel controlled at mile 10, that is when you can push. Every runner who banks time early pays it back after mile 10, usually with interest.

Check the forecast the night before. Warm, humid mornings cost real time, and the heat pace calculator will tell you how much to adjust before the gun rather than at mile 9.

What to do this week

1. Pick your race and count the weeks between now and then.
2. Write down your last four weeks of mileage and find your row in the table above.
3. Choose four or five running days you can actually keep, with the long run on the day you have the most time.
4. Slow your easy runs down until you can speak in full sentences.
5. Put the first workout on the calendar for next week, not this one.

If you would rather have someone set the length of the block, the paces and the long runs for you, and change them when a week goes sideways, that is what 1-on-1 coaching is for.

Written by

Coach Johnny Crain

2:12 marathoner. 4× US Olympic Marathon Trials qualifier. 4× NCAA national champion and 4× NCAA runner-up. Spoke at the RRCA National Convention. Founder and head coach at RunFitCoach, where he coaches every athlete personally.