12 Week Half Marathon Training Plan

Who this plan is for

Runners who already run every week and want a paced build-up to a half marathon: easy runs, a harder session on Tuesday, runs at half marathon pace and a long run on Sunday. The plan has 4, 5 or 6 runs a week, depending on your goal. It is not a beginner plan. If your goal is to finish, or you use walk breaks, the beginner half marathon plan fits better.

What you need before week 1 depends on your goal, because the plan’s first week is 65% of its biggest week. For a 2:00:00 goal:

• You run about 4 times a week, around 16.5 mi (27 km) in total.
• Your longest run in the last month is at least 5.5 mi (8 km).
• A recent race of about 56:47 for the 10K or 27:20 for the 5K. The plan closes the gap from there to the goal.

The box under the calculator shows the same three lines for your own goal.

The calculator takes half marathon goals from 1:10:00 to 2:30:00. Slower than that, the easy pace this method gives drops to a brisk walk, and the beginner half marathon plan is the better tool.

Check with a doctor before you start if you have a health condition, or if you are new to exercise.

How it works

This is a paced plan: every run has a distance and a pace, and all the paces come from one number, the VDOT score of your goal time. It is built by the same plan generator as the goal-time plans sold on this site.

• Three phases. Weeks 1 to 4 are easy running and the first threshold sessions. Weeks 5 to 8 add intervals and runs at half marathon pace. Weeks 9 to 12 hold the longest runs, then the taper.
• Paces that move up. Weeks 1 to 4 use the paces 2 VDOT points below your goal, weeks 5 to 8 one point below, weeks 9 to 12 the goal paces. Enter a recent race instead and the first phase uses the paces of that race, with a race-day target 2 points above it.
• The week. Tuesday is the main session: threshold running or intervals from week 3. Thursday is a run at half marathon pace in weeks 5, 6 and 11 and an easy run in the other weeks. Sunday is the long run. Every other running day is easy.
• Lighter weeks and a test. Week 4 drops back. Week 8 ends with a 10K race or time trial, and the plan gives the time that shows you are on track.
• Long runs with a fast finish. In weeks 7, 9 and 10 the last part of the long run is at half marathon pace.
• Long runs capped by time. The longest run is the shorter of a distance cap (19, 21 or 22 km, by goal) and a time cap (2 h 15 min at easy pace). A 2:30:00 goal tops out at 9.5 mi (15 km), a 1:30:00 goal at 13.5 mi (22 km).
• A two-week taper. For a 2:00:00 goal the last two weeks hold 75% and 30% of the peak week’s running, race not counted, and keep short sessions at speed.
• Limits on the steps. No long run or tune-up day is more than 1.5 miles (2 km) longer than the longest one before it, and no week is more than 20% bigger than the biggest week before it.

The formula

VDOT        = oxygen cost of your race speed
              ÷ share of your maximum you can hold that long
easy pace   = the speeds that cost 59% to 74% of VDOT
threshold   = the speed that costs 88% of VDOT
interval    = the speed that costs 97.5% of VDOT
race paces  = the race times with the same VDOT

weeks 1 to 4   paces for goal VDOT − 2
weeks 5 to 8   paces for goal VDOT − 1
weeks 9 to 12  paces for goal VDOT

from a recent race: goal VDOT = race VDOT + 2

The two equations behind VDOT are written out on the VO2 max calculator. They come from Jack Daniels and Jimmy Gilbert, and the training intensities from Daniels’ Running Formula.

Worked example

A goal of 2:00:00 for the half marathon.

1. Speed: 21,097.5 m ÷ 120 min = 175.8 m per minute.
2. That speed costs 30.66 ml/kg/min, and a runner can hold 84.1% of their maximum for 120 minutes. VDOT: 30.66 ÷ 0.841 = 36.5.
3. Weeks 1 to 4 use VDOT 34.5: easy runs at 10:35 to 12:37 per mile (6:35 to 7:51 per km), threshold at 9:14 per mile (5:44 per km).
4. Weeks 9 to 12 use VDOT 36.5: half marathon pace is 9:09 per mile (5:41 per km), threshold 8:50 per mile (5:29 per km).
5. The plan has 4 runs a week. It starts at 16.5 mi (27 km) a week and peaks at 24.2 mi (38.9 km), with a longest run of 12 mi (19 km).

How to pace each run

The table under the calculator gives your paces for each phase, and every session in the schedule prints the pace it needs. This is how each kind of run is meant to feel.

• Easy runs and long runs. Anywhere inside the easy range. The fast end is a ceiling, not a target, and the slow end is fine on tired days.
• Threshold repeats and tempo runs. The pace at 88% of your VDOT: hard but steady. Repeats have a short jog between them, about a minute for every five minutes of running. A tempo run is the same pace without the breaks.
• Intervals. Repeats of 800 to 1,200 m at the pace of 97.5% of your VDOT, with 2 or 3 minutes of easy jogging between. The last repeat should be as fast as the first.
• Half marathon pace runs. Race pace for the phase you are in, after an easy warm-up. In the last phase that is your goal pace: 9:09 per mile (5:41 per km) for 2:00:00.
• The tune-up race. A 10K at full effort in week 8. The plan prints the time that says you are on track. If you miss it by more than a couple of percent, keep the paces of weeks 5 to 8 for the rest of the plan and think about a slower goal.
• Race day. Start a few seconds per mile slower than goal pace for the first two miles, then settle. The pace band generator prints the splits for your wrist.

If you miss a week

• A day or two. Skip them and carry on. Do not squeeze a missed session into the next day, and do not run two hard days in a row.
• One week. If it was a recovery week, the tune-up week or a taper week, carry on with the next one. If it was a build week and your race date has room, pick up where you stopped and let the calendar slip a week. If the date is fixed, rejoin at the current week, keep the long run within 1.5 miles (2 km) of your longest run in the last four weeks, and swap that week’s Tuesday session for an easy run.
• Two weeks or more. Go back to the last week you finished and repeat it before moving on. If that leaves fewer weeks than the plan needs, the honest fix is a slower goal or a later race: change the goal or the date above and see what fits.
• Stopped by illness or pain. That is a question for a doctor or physiotherapist, not for a training plan.

What the research supports

Two parts of this plan lean on published studies. The rest is how the plan is built, not settled science.

• The taper. A meta-analysis of 27 studies of competitive athletes found the largest gains from a two-week taper in which training volume fell by 41 to 60% while intensity and the number of sessions stayed the same (Bosquet and colleagues, 2007). The last two weeks of this plan cut running by 47% on average for a 2:00:00 goal.
• The long-run steps. In a study that followed 5,205 runners for 18 months, the rate of overuse injury was higher after a run more than 10% longer than the runner’s longest run of the previous 30 days. Week-to-week changes in total distance showed no such link (Frandsen and colleagues, 2025). For a 2:00:00 goal the long runs here step up by 6 to 14% at a time, so 4 of the 6 steps are over that 10% line. If you have spare weeks before the race, repeating a week before a big step is the cautious choice.

The same plan as files

The goal-time plans we sell are this 12-week schedule fixed to one goal. What they add is a PDF in kilometer and mile editions, a calendar file that puts every session on the right day in Google, Apple or Outlook, and a printable pace band for race day.

• 1:45 Half Marathon Training Plan, $19. For runners who run about 5 times a week, around 20 mi in total.
• Sub-2 Hour Half Marathon Training Plan, $19. For runners who run about 4 times a week, around 16.5 mi in total.

Each of those pages shows two weeks of its plan and has the link to buy.

Print it or save it

The Print this plan button prints the plan alone: your paces, the overview and all 12 weeks, without the menus or the text on this page. Choose “Save as PDF” in the print dialog to keep a copy on your phone.

“Copy link to result” gives a link that reopens the page with your units, time and race date filled in. With a race date set, the page marks the current week each time you open it.

Questions

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Sources

1. Daniels J. Daniels’ Running Formula. 4th ed. Human Kinetics; 2022. VDOT tables and training intensities.
2. Daniels J, Gilbert J. Oxygen Power: Performance Tables for Distance Runners. 1979.
3. Bosquet L, Montpetit J, Arvisais D, Mujika I. Effects of tapering on performance: a meta-analysis. Medicine & Science in Sports & Exercise. 2007;39(8):1358-1365.
4. Schuster Brandt Frandsen J, Hulme A, Parner ET, et al. How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study. British Journal of Sports Medicine. 2025;59(17):1203-1210.