A Full Ironman is 3.8km of swimming, 180km of cycling, and a 42.2km run — back to back, on the same day. Training for one properly takes months. Training for one with the wrong plan can cost you your race before you even reach the start line.
I know because I’ve been there. DNF at Ironman Busselton 2024. I had a plan. It just wasn’t the right one for me.
This guide covers everything you need to build an Ironman training plan that actually works — how many weeks you need, how to structure each phase, what a real training week looks like, and the mistakes most age groupers make. If you’ve already done your research and just want a plan built around your specific fitness, schedule, and race date, irontri generates one for you automatically.
How long does an Ironman training plan need to be?
The honest answer depends on where you’re starting from. But here’s a simple framework:
- Already racing 70.3s regularly: 20–24 weeks is enough to make the step up to full distance.
- Solid base fitness, no recent triathlon racing: 28–32 weeks. You need time to build sport-specific endurance across all three disciplines before you start pushing volume.
- New to triathlon or returning from injury: 36–52 weeks. Trying to rush an Ironman build is one of the leading causes of race-day disasters and DNS/DNFs.
The minimum viable Ironman training plan is around 20 weeks — and that only works if you’re already in strong shape. Most age groupers benefit from 24–30 weeks. irontri builds your plan automatically from today to your race date, adjusting the structure based on your current fitness.
The 10% rule: Never increase your total weekly training volume by more than 10% from one week to the next. Breaking this rule is the single fastest way to end up injured before race day.
The four phases of an Ironman training plan
Every solid Ironman training plan is built around four phases. The weeks allocated to each phase shift depending on your total build time, but the structure stays the same.
| Phase | Focus | Typical Duration |
|---|---|---|
| Base | Aerobic base, form, injury-proofing. Low intensity, rising volume. | 8–12 weeks |
| Build | Threshold work, brick sessions, race-pace efforts. Volume peaks here. | 8–12 weeks |
| Peak | Highest volume weeks. Back-to-back long sessions. Race simulation. | 2–4 weeks |
| Taper | Volume drops 40–60%. Intensity maintained. Arrive fresh. | 2–3 weeks |
Base Phase
The base phase is where most athletes go wrong — they train too hard, too soon. The entire point of base is to build your aerobic engine at low intensity. Zone 2 heart rate across the board. Long, slow swims. Easy rides. Conversational-pace runs. It feels too easy, which is exactly right.
This phase also builds connective tissue strength and injury resistance. Rushing through it to get to the “real” training is how age groupers end up sidelined in week 14.
Build Phase
The build phase introduces race-pace work and brick sessions. Volume is still rising, but now you’re mixing in threshold intervals on the bike, tempo runs off the bike, and longer open-water swims. This is where your fitness actually develops.
Brick sessions — bike followed immediately by run — are mandatory from the build phase. Your legs need to learn how to run when they feel like concrete. One brick session per week is enough; more than that becomes counterproductive.
Peak Phase
Peak is where the big weeks happen. Long rides up to 5–6 hours. Runs up to 30–35km. Back-to-back long sessions on the weekend. This is the hardest part of the plan and where athletes are most tempted to skip sessions — don’t. These weeks are what carry you through kilometres 120–180 of the bike and kilometres 30–42 of the run.
Taper Phase
You cannot gain fitness in the taper. But you can absolutely wreck your race by not tapering properly. Volume drops significantly — 40 to 60% — while intensity stays the same. Your body is consolidating months of training. Trust it. The heavy legs and weird moods during taper are completely normal.
What a training week actually looks like
A typical Ironman training week has 9–12 sessions across the three disciplines, plus one rest day. Here’s an example build-phase week for an athlete with around 12–14 hours available:
Monday — Rest
- Full rest. Foam roll, sleep, eat.
Tuesday — Swim + Run
- AM: 3km pool swim with intervals (e.g. 10 x 200m at threshold pace)
- PM: 50–60 min easy Zone 2 run
Wednesday — Bike
- 90 min ride including 3 x 15 min at race-pace watts (Zone 3–4)
Thursday — Swim + Run
- AM: 3.5km open-water or masters swim
- PM: 45 min easy run
Friday — Bike or Rest
- 60 min easy Zone 2 ride (or full rest if legs are heavy)
Saturday — Long Brick
- 4–5 hr bike ride at race effort, immediately followed by 30–45 min run
Sunday — Long Run
- 2–2.5 hr easy run (Zone 2, conversational pace)
This is a template — not a prescription. Your actual sessions should be calibrated to your FTP, lactate threshold pace, and swim CSS. irontri pulls this data directly from Strava and builds every session around your specific numbers.
The most common Ironman training plan mistakes
1. Treating all weeks equally
Every third or fourth week should be a recovery week — volume drops 20–30% to let your body absorb the load. Athletes who skip recovery weeks accumulate fatigue that compounds over months and either get injured or show up to race day already depleted.
2. Ignoring the swim until it’s too late
The swim is the shortest leg, so it gets deprioritised. But a rough swim — panic, poor pacing, going out too hard — spikes your heart rate and burns glycogen you need for the next 10 hours. Swim twice a week minimum, every week of your build.
3. Generic paces and power targets
Most free Ironman training plans give you generic targets like “Zone 2” or “race pace” without defining what that means for you specifically. If your Zone 2 heart rate is 135 bpm and you’re riding at 155, you’re building fatigue, not aerobic base. Your plan needs to be calibrated to your actual numbers.
4. Not practising race nutrition
You need 400–500 calories per hour on the bike for a full Ironman. Your gut needs to be trained to handle this while your body is working hard. Start practising your nutrition strategy in long sessions from the build phase, not the week before your race.
5. A plan that doesn’t fit your life
A plan that has you training 14 hours a week when you can realistically do 10 is worse than useless — it sets you up to fail every week and erodes motivation. Your Ironman training plan needs to be built around your actual available hours, your work schedule, your family commitments, and your recovery capacity.
FIFO athlete? Training for an Ironman on a fly-in fly-out roster adds another layer of complexity — restricted gym access on-site, the physical toll of the work itself, and irregular weeks. Read the full guide to FIFO Ironman training here.
How irontri builds your Ironman training plan
Generic training plans are built for a hypothetical athlete. irontri builds your plan for you.
When you sign up, irontri asks about your race date, your current fitness level, your available training hours per week, your work schedule (including FIFO rosters), and your target finish time. If you connect Strava, it automatically pulls your actual run pace, bike FTP, and swim data to calibrate every session to your real numbers.
Your plan is then generated week by week, phased correctly from today to race day, with sessions that scale to your distance — whether you’re targeting a 10-hour finish or pushing for a sub-9. Every week builds on the last. Recovery weeks are built in automatically. And if life gets in the way, you can swap sessions around without wrecking the structure.
Over 500 athletes across 51 countries are currently training with irontri plans. It’s free to start.
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Build my plan →Frequently asked questions
Can a beginner complete a Full Ironman?
Yes — with enough time and the right plan. If you can currently run 10km and swim 1km without stopping, you have a workable base. Give yourself at least 10–12 months if you’re coming from minimal triathlon experience. Attempting to rush the build is the main reason beginner Ironman attempts end in injury or DNF.
How many hours a week do you need to train for an Ironman?
Most age groupers train between 10 and 15 hours per week at peak. The minimum to finish an Ironman comfortably is around 8–10 hours per week consistently across your build. Elite age groupers often train 16–20 hours, but that’s not realistic or necessary for most people.
What’s the difference between an Ironman training plan and a 70.3 plan?
Volume, primarily. A 70.3 plan typically peaks at 10–12 hours per week. A full Ironman plan peaks higher — and the long sessions are significantly longer. The bike leg alone doubles from 90km to 180km. Your plan also needs more recovery weeks and a longer taper to arrive at the line fresh after months of much higher load.
Do I need a coach for an Ironman?
A coach helps, but isn’t essential — especially if you have a well-structured personalised plan and the discipline to follow it. What you do need is a plan that’s actually built for you, not a generic PDF downloaded from the internet. That’s exactly what irontri is designed to do.
What happens if I miss weeks of training?
Life happens. Missing one or two weeks won’t ruin your race — consistency over months matters more than perfection in any single week. If you miss more than that, reassess your timeline. It’s better to defer your race than to arrive undertrained.