Ironman Training Plan: A 20-Week Full Distance Plan With Fueling
A free 20-week Ironman training plan for athletes with a 70.3 or Olympic distance behind them. Five phases from 8 to 16 hours a week, the long ride, long run, and brick for every week, a sample peak week, how to scale it, and how to eat enough to absorb 15 hour training weeks.
Quick answer
A 20-week Ironman training plan builds from about 8 to 16 hours a week in five phases: base (weeks 1 to 4), build 1 (weeks 5 to 8), build 2 (weeks 9 to 12), peak (weeks 13 to 17), and taper (weeks 18 to 20), with a lighter week every fourth week. The key sessions are a long ride that grows to 5.5 to 6 hours, a long run that tops out at about 2.5 hours, a weekly brick, and three swims. Keep about 80 percent of training easy. On 15 hour weeks, eat 8 to 12 g of carbs per kg on long ride days, practice 60 to 90 g of carbs per hour on every long ride, and take about 0.3 g of protein per kg after key sessions, so you do not slide into low energy availability.
An Ironman is a 3.8 km (2.4 mi) swim, a 180 km (112 mi) bike, and a 42.2 km (26.2 mi) run, with a 17 hour cut-off. This 20-week Ironman training plan builds from about 8 to 16 hours a week in five phases: base, build 1, build 2, peak, and taper. The key sessions are a long ride that grows to 6 hours, a long run that tops out at 2.5 hours, a weekly brick, and three swims. Every fourth week is lighter.
The plan gives you the hours and sessions for all 20 weeks. It also covers what decides whether you absorb them: food. At 15 hours a week you burn thousands of extra calories, and under-eating is one of the most common ways a full-distance build goes wrong. The long rides are also your rehearsal for race fueling. The race-day plan itself is in our Ironman nutrition plan, linked at the end.
The Plan at a Glance
| Phase | Weeks | Hours per week | Focus |
|---|---|---|---|
| Base | 1 to 4 | 8 to 10 (7 in week 4) | Aerobic volume, swim technique, strength |
| Build 1 | 5 to 8 | 10.5 to 12.5 (8.5 in week 8) | Longer rides, threshold intervals, first bricks, gut training starts |
| Build 2 | 9 to 12 | 12.5 to 14.5 (9.5 in week 12) | Race-effort blocks, long run to 2 hours, 60 g carbs per hour on long rides |
| Peak | 13 to 17 | 15 to 16 (10 in week 16) | 5 to 6 hour rides, longest runs, full race rehearsals |
| Taper | 18 to 20 | 11, then 8, then about 4.5 plus the race | Volume falls, short race-effort blocks stay |
Who This Plan Is For
- You have finished a 70.3, or at least an Olympic distance triathlon.
- You can swim 2,000 m (1.2 mi) without stopping, ride for 3 hours, and run 15 km (9.3 mi).
- You already train about 7 to 8 hours a week.
- You can find 15 to 16 hours in the peak weeks, including one 6 to 7 hour weekend day.
If you are starting from scratch, give yourself 9 to 12 months and race a 70.3 first. If you have a heart condition or other medical condition, or you get chest pain, dizziness, or palpitations in training, see a doctor before you go further.
How Hard to Go
An Ironman is an aerobic race. Successful endurance athletes do about 80 percent of their sessions at low intensity and about 20 percent hard, so most hours here are in Zone 2, where you can talk in full sentences (about 65 to 78 percent of max heart rate, RPE 3 to 4 out of 10). Race effort in this plan means the effort you could hold for the whole bike leg: the top of Zone 2, RPE 4 to 5. Threshold work is Zone 4 (85 to 92 percent of max, RPE 7 to 8), in blocks of 10 to 20 minutes, once or twice a week.
The 20-Week Ironman Training Plan, Week by Week
| Week | Phase | Hours | Long ride | Long run | Key session |
|---|---|---|---|---|---|
| Week 1 | Base | 8 | 2:30 | 60 min | Swim drills plus 10 x 100 m; two strength sessions |
| Week 2 | Base | 9 | 2:45 | 65 min | Bike 4 x 8 min Zone 3; strides after easy runs |
| Week 3 | Base | 10 | 3:00 | 75 min | Swim 2,000 m continuous; bike 3 x 12 min Zone 3 |
| Week 4 | Recovery | 7 | 2:00 | 50 min | Tests: 400 m swim, 20 min bike, 5 km run |
| Week 5 | Build 1 | 10.5 | 3:15 plus 15 min run | 80 min | Bike 3 x 10 min Zone 4; swim 8 x 200 m |
| Week 6 | Build 1 | 11.5 | 3:30 plus 20 min run | 90 min | Run 3 x 10 min Zone 3 to 4 |
| Week 7 | Build 1 | 12.5 | 4:00 plus 20 min run | 1:40 | Bike 2 x 20 min Zone 4; swim 3,000 m continuous |
| Week 8 | Recovery | 8.5 | 2:30 | 60 min | Repeat the tests; first open water swim |
| Week 9 | Build 2 | 12.5 | 4:15 plus 20 min run | 1:45 | Long ride with 2 x 30 min at race effort |
| Week 10 | Build 2 | 13.5 | 4:30 plus 30 min run | 1:55 | Swim 5 x 400 m; run 2 x 20 min Zone 3 |
| Week 11 | Build 2 | 14.5 | 5:00 plus 30 min run | 2:00 | Long ride with 3 x 30 min at race effort |
| Week 12 | Recovery | 9.5 | 3:00 | 75 min | Easy week; test race kit |
| Week 13 | Peak | 15 | 5:00 with 2 hours at race effort, plus 30 min run | 2:15 | Open water 3,000 m; bike 3 x 20 min Zone 3 |
| Week 14 | Peak | 16 | 5:30 plus 45 min run | 2:30 | Longest run, last 30 min at race effort |
| Week 15 | Peak | 16 | 6:00 race rehearsal plus 30 min run | 1:45 | Full race fueling for 6 hours |
| Week 16 | Recovery | 10 | 3:00 | 75 min | Easy week, sleep, eat well |
| Week 17 | Peak | 15 | 5:00, last 2 hours at race effort, plus 60 min run | 1:45 | Last big brick, three weeks out |
| Week 18 | Taper | 11 | 4:00 | 1:30 | Race-effort blocks stay, volume drops |
| Week 19 | Taper | 8 | 3:00 with 3 x 20 min race effort | 60 min | Short swims at race pace |
| Week 20 | Race week | About 4.5 plus the race | 60 to 75 min with 3 x 5 min race effort | 30 to 40 min with strides | Short swim, ride, and run the day before; race |
A normal week has 9 to 11 sessions: three swims of 2,500 to 3,500 m, three or four rides, three runs, and one or two short strength sessions until week 12. You never ride 180 km and run a marathon in training. The longest run stays at 2.5 hours because longer runs add injury risk faster than fitness. Week 18 is a step down after the last big weekend. Weeks 19 and 20 are the real taper, where volume falls by about half and then more. A meta-analysis of 27 studies found that cutting volume by 41 to 60 percent while keeping some intensity works best.
Key Sessions in Each Phase
| Phase | Swim | Bike | Run | Brick |
|---|---|---|---|---|
| Base | Drills, 10 x 100 m, build to 2,000 m continuous | Zone 2 long ride, short Zone 3 blocks | Zone 2 runs with strides | None yet |
| Build 1 | 8 x 200 m hard; 3,000 m continuous | 3 x 10 to 2 x 20 min in Zone 4 | 3 x 10 min Zone 3 to 4; long run to 1:40 | Long ride, then 15 to 20 min run |
| Build 2 | 5 x 400 m at race pace; open water | 2 to 3 x 30 min race effort inside the long ride | Long run to 2 hours, Zone 2 | Long ride, then 20 to 30 min run |
| Peak | 3,000 to 3,800 m open water in your wetsuit | 5 to 6 hour rides with 2 hours at race effort | Long run to 2:30, last 30 min at race effort | Long ride, then 30 to 60 min run with race fueling |
| Taper | Shorter swims, race-pace 100s | Shorter rides, 20 min race-effort blocks | Short runs with strides | One short brick 10 days out |
A Sample Peak Week (Week 14, About 16 Hours)
| Day | Session | Time |
|---|---|---|
| Monday | Swim 3,000 m easy with drills | 1:00 |
| Tuesday | Bike 3 x 15 min in Zone 4, then 20 min easy run | 1:50 |
| Wednesday | Swim 3,500 m with 5 x 400 m at race pace; 50 min Zone 2 run | 2:00 |
| Thursday | Bike Zone 2 with 4 x 10 min at race effort | 1:30 |
| Friday | Swim 3,000 m continuous, open water if you can | 1:00 |
| Saturday | Long ride 5:30 in Zone 2, last 90 min at race effort, then 45 min run | 6:15 |
| Sunday | Long run 2:30 in Zone 2, last 30 min at race effort | 2:30 |
Saturday and Sunday together are almost 9 hours. That weekend is the core of Ironman fitness, and it is also where fueling matters most, because you start Sunday on whatever you ate after Saturday.
How to Scale the Plan
| What changes | About 10 to 12 hours at peak | About 16 to 18 hours at peak |
|---|---|---|
| Weekly hours | About 70 percent of each week: 6 in base, 11 to 12 at peak | Add 1 to 2 hours a week from week 9, mostly easy riding |
| Long ride | Cap at 4:30 to 5:00 | Up to 6:00 to 6:30 |
| Long run | Cap at 2:00 | Still cap at 2:30; add a short run, not a longer one |
| Swims | 2 a week, about 3,000 m each | 3 to 4 a week |
| Keep no matter what | Long ride, long run, brick, one Zone 4 ride | Same |
| Cut first | Third swim, easy midweek run, strength | Easy volume before quality |
Twelve hours at peak gets many athletes to the finish. If you miss a week through illness, repeat the week before it rather than jumping ahead.
The Fueling Layer: Eat for the Training You Do
At 15 to 16 hours a week, training alone burns roughly 8,000 to 10,000 kcal. For a 70 kg (154 lb) athlete that puts average needs at about 3,300 to 3,700 kcal a day, and far more on the long ride day. Your appetite may not keep up on its own, because hard sessions can blunt hunger for a while. So plan the food the way you plan the sessions.
| Day type | Training | Carbs per kg | Rough energy for a 70 kg athlete |
|---|---|---|---|
| Rest or easy swim | 0 to 1 hour | 3 to 5 g (210 to 350 g) | 2,300 to 2,800 kcal |
| Midweek day | 2 to 3 hours with intervals | 6 to 8 g (420 to 560 g) | 3,300 to 4,000 kcal |
| Long ride or big brick | 5 to 7 hours | 8 to 12 g (560 to 840 g) | 5,000 to 6,500 kcal |
The carb ranges come from the sports nutrition position stand of the American College of Sports Medicine and its dietitian partners. The energy figures are estimates; your weight trend over a few weeks tells you more. On a long ride day, a third or more of those calories can come from what you eat on the bike: 80 g of carbs an hour for 5.5 hours is 440 g, or about 1,760 kcal.
Long Ride Fueling: Rehearse 60 to 90 g per Hour
| Ride length | Carbs per hour | Total carbs | Fluid and sodium per hour |
|---|---|---|---|
| 3 hours | 60 g | About 180 g | 400 to 800 ml, 300 to 600 mg sodium |
| 4 hours | 60 to 75 g | 240 to 300 g | 400 to 800 ml, 300 to 600 mg sodium |
| 5 hours | 70 to 90 g | 350 to 450 g | Same, more sodium in heat or if you sweat salty |
| 6 hours | 70 to 90 g | 420 to 540 g | Same, and plan where you refill bottles |
Eat 1.5 to 3 g of carbs per kg 2 to 4 hours before a long ride, start eating in the first 20 to 30 minutes, then take something every 15 to 20 minutes. Above 60 g per hour, use products that mix glucose and fructose. Glucose alone is absorbed at about 60 g per hour. Take a gel about 10 minutes before you get off the bike for the brick run.
The Gut-Training Progression
Your gut adapts to what you feed it during exercise. Regular practice speeds up stomach emptying, reduces fullness, and raises the number of carb transporters in the gut. Most triathletes can learn to take 60 to 90 g per hour from mixed carb sources. Build it like any other fitness.
| Weeks | Long ride target | Long run target | Focus |
|---|---|---|---|
| 1 to 4 | 40 to 50 g per hour | 20 to 30 g per hour on runs over 75 min | Find drinks and gels you like |
| 5 to 8 | 50 to 60 g per hour | 30 g per hour | Add glucose plus fructose products |
| 9 to 12 | 60 to 75 g per hour | 30 to 45 g per hour | Switch to your race products |
| 13 to 17 | 75 to 90 g per hour | 45 to 60 g per hour | Full rehearsals at race effort, in race heat if you can |
| 18 to 20 | Race target on shorter rides | Race target | Nothing new |
Rate your stomach from 0 to 10 after each long session. If it goes above 3, stay at the same step for another week. The week 15 ride is your dress rehearsal: same breakfast, same start time if you can, same bottles and gels, same timing.
Avoid Low Energy Availability (REDs)
Energy availability is what is left from the food you eat after training, per kg of fat-free mass. When it stays too low, the body cuts back on repair, hormones, bone, and immunity. The International Olympic Committee calls the result Relative Energy Deficiency in Sport, or REDs, and it affects men and women. In a lab study of women, hormone pulses changed within 5 days when energy availability fell below 30 kcal per kg of lean mass per day. A 70 kg athlete with 58 kg of lean mass who eats 3,500 kcal on a day that burns 2,500 kcal in training is at about 17 kcal per kg. On one day that is fine. Week after week it is not.
- Warning signs: missed or irregular periods, low sex drive, frequent colds, bone stress injuries, poor sleep, low mood, feeling cold, and sessions getting worse despite training.
- Fuel during long sessions. Carbs on the bike count, and they cut the gap you have to close afterwards.
- Do not diet in the build or peak. If you want to lose weight, do it slowly in the base phase.
- Weigh yourself once a week. A steady drop you did not plan is a sign to eat more.
- Missed periods for three months, a bone stress injury, or ongoing fatigue need a doctor, and ideally a sports dietitian.
Recovery Protein and Carbs
Aim for 1.2 to 2.0 g of protein per kg a day, spread over four or five meals of about 0.3 g per kg. For a 70 kg athlete that is about 21 g per meal and 84 to 140 g a day. Have one of those meals within an hour or two of every key session, with plenty of carbs. After the Saturday brick, eat a full carb and protein meal, then a carb-rich dinner and a snack before bed, so you start the Sunday long run fueled. If you train again within 8 hours, take 1 to 1.2 g of carbs per kg per hour for up to 4 hours.
Race Week in Short
| When | Target | Note |
|---|---|---|
| Weeks 18 to 20 | 5 to 7 g carbs per kg most days | Training drops, but do not diet |
| Last two days | 8 to 10 g carbs per kg per day | Low fiber and fat, carb drinks help |
| Breakfast, 3 to 4 hours before | 1.5 to 3 g carbs per kg | The breakfast from your week 15 rehearsal |
| Bike and run | 60 to 90 g per hour on the bike, less on the run | Only what you practiced |
The full race-day plan, from special needs bags to a sample 12 hour race, is in our Ironman nutrition plan, linked at the end. Juggling a different carb target for every day of a 20-week build is the kind of math Mavr does from your synced training.
A 15 hour week needs different food on a swim day, a 6 hour ride day, and the day after. Mavr syncs your sessions from Garmin, TrainingPeaks, Strava, or Intervals.icu, sets carbs, protein, and fat for each day, and plans carbs, fluid, and sodium for every long ride and brick.
Frequently Asked Questions
How many hours a week should I train for an Ironman?
Most age-group athletes train 8 to 10 hours a week in base and 12 to 16 hours in the peak weeks. About 10 to 12 hours at peak can get you to the finish if you already have a 70.3 behind you. More hours help most when they are easy riding.
Is 20 weeks enough to train for an Ironman?
Yes, if you start able to swim 2,000 m, ride for 3 hours, and run 15 km, and you already train 7 to 8 hours a week. If you are new to triathlon, plan on 9 to 12 months and race a 70.3 first.
How long should my longest ride and run be?
Build the long ride to 5.5 to 6 hours, which is 150 to 180 km for most athletes, and the long run to about 2.5 hours. You do not need to run a marathon in training. Weekly bricks and back-to-back weekend sessions do that job with less injury risk.
How many calories do I need when training for an Ironman?
At 15 to 16 hours a week, a 70 kg athlete needs roughly 3,300 to 3,700 kcal a day on average, from about 2,300 on rest days to 5,000 or more on long ride days. Carbs should run from 3 to 5 g per kg on rest days to 8 to 12 g per kg on the biggest days.
How do I train my gut for an Ironman?
Start at 40 to 50 g of carbs per hour on long rides in the base phase and add about 10 to 15 g every few weeks, reaching 75 to 90 g per hour in the peak weeks. Use glucose plus fructose products above 60 g per hour, practice at race effort, and use your race products from week 9.
Should I try to lose weight while training for an Ironman?
Not in the build or peak phases. Cutting calories in 15 hour weeks raises the risk of illness, injury, and low energy availability. If you want to lose weight, do it slowly in the base phase and keep carbs around your key sessions.
Sources
Sources and official references
- 1.Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic PerformanceJournal of the Academy of Nutrition and Dietetics (Thomas et al., 2016) · Daily carbs of 3 to 5 g/kg on light days up to 8 to 12 g/kg on very high training days; protein 1.2 to 2.0 g/kg and 0.3 g/kg per meal; recovery carbs of 1 to 1.2 g/kg per hour
- 2.Fueling the Triathlete: Evidence-Based Practical Advice for Athletes of All LevelsCurrent Sports Medicine Reports (Getzin et al., 2017) · Triathletes can usually tolerate 60 to 90 g of carbs per hour from multiple carb sources
- 3.Training the Gut for AthletesSports Medicine (Jeukendrup, 2017) · Gastric emptying, fullness, and intestinal carb absorption adapt to regular carbohydrate intake
- 4.2023 International Olympic Committee's (IOC) Consensus Statement on Relative Energy Deficiency in Sport (REDs)British Journal of Sports Medicine (Mountjoy et al., 2023) · Low energy availability harms health and performance in female and male athletes
- 5.Luteinizing Hormone Pulsatility Is Disrupted at a Threshold of Energy Availability in Regularly Menstruating WomenJournal of Clinical Endocrinology and Metabolism (Loucks and Thuma, 2003) · Hormone pulses changed within 5 days below 30 kcal per kg of lean mass per day
- 6.What Is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?International Journal of Sports Physiology and Performance (Seiler, 2010) · Successful endurance athletes do about 80 percent of sessions at low intensity
- 7.Effects of Tapering on Performance: A Meta-AnalysisMedicine and Science in Sports and Exercise (Bosquet et al., 2007) · A taper cutting volume by 41 to 60 percent while keeping intensity gave the best results
Prompt ideas for AI assistants
- “Adapt this 20-week Ironman plan to 12 hours a week at peak.”
- “How many carbs and calories should I eat on a 6 hour ride day at 75 kg?”
- “Plan my gut training to reach 90 g of carbs per hour on the bike by week 15.”
Mavr syncs your Ironman plan from Garmin, TrainingPeaks, Strava, or Intervals.icu, sets carbs, protein, and fat for every training day, and plans carbs, fluid, and sodium per hour for each long ride and brick.
Written by
Mavr Sports Nutrition Team
The Mavr sports-nutrition team translates peer-reviewed endurance research (Jeukendrup, Burke, the ISSN) into daily fueling for runners and triathletes.