Most "12-week plans" online are a table of distances with no logic behind them: week 6 is bigger than week 5 because, sure, why not. This one isn't that. Every week here exists because of the week before it and the week after it. Here's the full breakdown, week by week, so you can see the shape of it before you commit to a single session.
I build this structure with my 1:1 athletes all the time, and it's the same one behind RunLetters coaching. Twelve weeks, three phases, a repeating build-and-deload rhythm, and a long run that climbs toward a real peak instead of just getting randomly longer. No spreadsheet panic required, just read it top to bottom once and you'll understand exactly why each week is doing what it's doing.
Twelve weeks is the beginner minimum, the shortest runway where you can move through Base, Support, and Specific phases without skipping the parts that matter. This particular plan is written a notch above pure beginner: it assumes you can already comfortably run 8km, you're training 4-5 days a week already, and you've got at least a few months of consistent running behind you. If that's you (beginner-to-intermediate, building toward a stronger half rather than just surviving one), this is your plan.
If you're starting closer to zero (you're not running consistently yet, or 8km sounds like a lot right now), go read the couch-to-half-marathon guide first. It's not a lesser version of this plan, it's the right version for where you are, and it'll get you to the point where this 12-week structure makes sense to start.
This plan runs in blocks of four weeks: three weeks of building load, then one week of deliberately backing off. Three build weeks, one deload, repeat. It's not a nice-sounding cycle I picked for symmetry, it's how the body actually adapts. You don't get fitter during the hard weeks, you get fitter in the recovery that follows them. Stack three build weeks without a real break and you're just accumulating fatigue that shows up as flat legs, bad sleep, or a nagging ache by week 7.
Across 12 weeks that gives you exactly three blocks:
Deload weeks aren't "easy weeks" in a vague sense: they cut long run distance by roughly 30% versus the week before, and trim everything else too. You'll still run, still do a shorter quality session, still hit the gym. It just all gets smaller for seven days so the next block can start from a rested base instead of a depleted one.
Phase moves from Base (wide, aerobic, habit-building) to Support (bridging toward race demands) to Specific (race-rehearsal sharp). Long run climbs from 8km toward a peak of 18km in week 11, with weeks 4 and 8 pulled back roughly 30% as scheduled deloads. Quality sessions stay at 1 a week through most of the plan and can step up to 2 once you're handling week 5-6 comfortably, never more than that, and never on the day before or after the long run.
| Week | Phase | Long run | Notes |
|---|---|---|---|
| Week 1 | Base | 8km | Easy running dominates. One quality session (short strides or light progression). Strength ×2 begins now, not "once you're settled in." |
| Week 2 | Base | 9km | Same shape as week 1, small bump in volume. Quality session stays short: this is about consistency, not intensity. |
| Week 3 | Base | 10km | Peak of block 1. First progression run of the plan: easy start, faster finish, nothing dramatic. Strength ×2 continues. |
| Week 4 | Base (deload) | 7km | Deload. Long run drops about 30% from week 3's 10km. Quality session shortens too. This week is a checkpoint, not a punishment. |
| Week 5 | Support | 11km | Support phase opens: sessions start pointing toward race demands. Speed volume nudges up, capped at +5 minutes versus last week's total. |
| Week 6 | Support | 12km | Second progression run lands here (your 2-per-plan minimum is now met). Strength stays at 2x: don't let it slide as running gets more real. |
| Week 7 | Support | 13km | Peak of block 2. If you're handling the week 5-6 load well, this is where a second quality session can be added, never back-to-back with the long run. |
| Week 8 | Support (deload) | 9km | Deload. Long run drops about 30% from week 7's 13km. Back to one quality session this week, kept short. Absorb the last three weeks before Specific begins. |
| Week 9 | Specific | 14km | Specific phase: sessions start looking like actual race demands, sustained efforts at closer to goal pace, not just easy miles with a hard day bolted on. |
| Week 10 | Specific | 16km | Long run climbing toward peak. Quality session mirrors race rhythm: think tempo blocks, not intervals. Strength still 2x, slightly lighter loads. |
| Week 11 | Specific | 18km | Peak long run of the whole plan: around 85% of race distance, as far as you go before race day. Nothing new gets introduced from here, only sharpening. |
| Week 12 | Race week | 3-4km shakeout + race | Not a deload: race week runs on its own logic. Volume drops hard, a few short strides keep legs sharp, strength goes to light maintenance only. Full detail in the taper guide and the taper planner. |
Two strength sessions a week run underneath this entire plan, from week 1 through week 11: squats, single-leg work, core, hip and glute strength, nothing that needs a personal trainer to explain. It's not filler for weeks when running feels light. Stronger hips and a stronger core are what keep your form together at km 18, when everything else in your body is arguing with you. In week 12, strength drops to light maintenance, just enough to keep things activated, not enough to leave any soreness behind before race day.
Week 12 is deliberately not treated as a fourth deload in this table, because it isn't one. A deload is about absorbing recent training load. Race week is about arriving at the start line fresh, with your fitness already banked from the eleven weeks before it: you can't add fitness in these final days, you can only take away freshness by trying. That's a different job, and it deserves its own guide rather than a squeezed-in paragraph here. Use the half marathon taper guide for the reasoning and the taper planner to get your exact day-by-day plan for the final stretch.
Yes, if you're already running 3-4 times a week and comfortable with 8km. It's the minimum window that lets you move through Base, Support, and Specific phases with two real deload weeks built in. If you're starting from less than that, use the couch-to-half-marathon guide first.
A planned drop in load, not just a rest week. Weeks 4 and 8 here cut the long run by roughly 30% versus the week before, plus trim the rest of the volume: a checkpoint that lets your body absorb the last three weeks before the next block starts.
This plan peaks at 16-18km around week 10-11, roughly 75-85% of race distance. You don't need to run the full 21.1km in training. See the taper planner for how it steps back down from there into race week.
This structure is the same one behind RunLetters Half Marathon Coaching, with a real coach (me, 13 half marathons in, PB 1:23:45) building your Base-Support-Specific blocks around your real schedule and adjusting as training actually goes, not just handing you a static PDF.
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