Many who are new to the sport, or at least considering it, will want to know how long it takes to train for an Ironman. This is a very reasonable question to ask, as It will dictate whether someone signs up for a race or not.
Unfortunately this is a very difficult question to answer. If someone hasn’t run since they were at school, is terrified of water and is clinically obese, they’re going to be on a very different journey from someone who wants to transition from running marathons to Ironman. To make things easier and fairer, I’m going to go by each discipline on a sport by sport basis to give you a rough idea on how long you need to prepare for each discipline.
Before we dive in though, I want to make two points. The first one is, right now can you even walk for 17 hours? This is the maximum time allowed to complete most official Ironman events. If the answer is no, then you’re going to be a long way from an Ironman. Yes, anyone’s legs get stiff and sore after walking for that long, but if you know you would struggle to keep your body moving for more than a few hours without getting horribly out of breath, you have a long road ahead.
The second point to make is that it took me eight years from starting the sport to crossing my first Ironman finish line. I could have probably done it within a year if I really, really wanted, but I was too busy winning smaller events and setting PBs in shorter events to worry about Ironman. It may be that to you Ironman is triathlon and you see no value in shorter events, but racing at a high level takes years of discipline and hard work, not just one year of hard work.
Swimming
For most athletes, the swim is going to be the most challenging discipline to learn and prepare for. Primarily because they can’t swim for toffee when they put their credit card details into the Ironman website. That’s not to say that they couldn’t thrash their way from one end of the pool to the other, but 3800M in open water? That’s a different kettle of fish entirely.
You need to learn to breathe when swimming freestyle, develop your catch, get your body rotation dialled in and learn to sight so you can see where you’re swimming. Not to mention making your way round this course surrounded by thousands of threshing limbs, waves, and being unable to se the bottom while encased a tight fitting rubber wetsuit. Has this paragraph made you break out in a cold sweat? You may be a good couple of years from taking on an Ironman.
Very few people go into the sport as established open water swimmers so you’ll be in good company taking on the journey to open water confidence with thousands of others.
Remember, the Ironman swim has a cutoff of two hours and twenty minutes, so while you need to finish within this time, you also really want to be closer to 90 minutes to buy you more time to finis the rest of the race comfortably.
Cycling
Of the three disciplines, cycling probably takes the shortest amount of time to develop, but requires the largest amount of hours to dedicate to ensure your improvement stays on track. You have ten hours and thirty minutes at most events to complete the swim, T1 and the bike, so you could be on the bike for up to eight hours, maybe longer. While you don’t necessarily need to hit an eight hour ride in training, you can’t get away with a handful of two hour rides. You’ll probably be looking to head out for 3-4 hour rides most weeks at a minimum as you approach your race.
Not only do you need to develop your leg strength and aerobic fitness, you also need to learn how to ride your bike confidently, develop your posterior resilience so you can spend eight hours sat in the saddle, and learn how to fix basic mechanicals. If you can’t so much as repair a puncture or dropped chain because you did all your riding on an indoor bike, you’re going to be at risk of all your money and training invested going up in a puff of smoke, or more accurately a hiss of air escaping from your tyre.
Cycling is a beautiful sport, but we need to invest some real time and effort in learning its intricacies before we can ride confidently.
For someone who is a confident, albeit out of shape cyclist who can’t ride for much more than an hour, you’re probably looking at approximately nine months to a year of development before they can confidently ride an Ironman bike course without flirting with the cutoffs, and still run a strong marathon.
Running
Running is the sport which will take the longest amount of time to get up to scratch if you want to have a successful Ironman. The reason for this is the high risk of injury, and the steep adaptation curve that comes with the sport. If you were to offer someone 10 million pounds/dollars to swim 3.8KM they would have a go by swimming heads up breaststroke. If you offered someone the same amount of cash to cycle 180KM, they would push it up the hills and it could take them the best part of 24 hours, but most people would be able to get it done.
However, if you were to ask someone to run a marathon off the back of a 3.8KM swim and 180KM bike ride, finishing with the cutoffs for 100 million, most people simply couldn’t. Their legs would most likely give out on them and cramp up, they would find themselves vomiting repeatedly, staggering from side to side as they hallucinate, and ultimately collapsing in a heap. An Ironman marathon is a war of attrition, and about much more than simple stubbornness.
Now, the average walking speed is 5KM/H, which means a marathon could be walked just under 8.5 hours. You have 6.5 hours to complete the run, so while you can’t afford to walk it at a leisurely pace, you can walk large chunks of it. That being said, if you’re reading this, you don’t want to walk the majority of the marathon, and I don’t want you to walk the majority of the marathon. There will most likely be walking breaks as you pass aid stations, but we want at least 20-30KM of good running before the lights start to go dark and we’re forced to go into survival mode, spending more time walking than running.
Speed isn’t really a concern here, it doesn’t matter how light you are or how fast you can run a 5K, this is about resilience and endurance, which takes a long time to develop. We’re talking months on end just accumulating time on feet, slowly increasing running volume.
Asking someone to run a marathon to win a silly amount of money works as a metaphor as a one day challenge, but successful run training requires months, probably years of gentle increases to volume and intensity. There’s a reason nobody explodes onto the competitive running scene out of nowhere, it’s a long, long journey to get good.
Think about your standard city centre marathon (not Boston). If you pop down to spectate you will see a small group of elite runners come through finishing in under three hours, then a huge surge around the four hour mark, which is the average finishing time. After this, there is a long, long trickle of competitors coming in at around five, six, seven, maybe even eight hours or more.
These are people who signed up for the marathon moths ago, but are walking the majority of their way round. Some of them may suffer with disbilities or other issues which would prevent them from running a marathon in a traditional fashion, but the majority will have underestimated just how difficult a marathon is. They may have got injured in their training (which is often a sign of poor strength, which you’ll also need to work on), or their body may just not be ready. If you try to just push through on willpower and stubbornness the chances are you will get found out.
If someone is training for a marathon from scratch, I would allow at least six months from the date of signing up for the race to being able to run the race nonstop. This could be a year or even longer if they are especially unfit or lacking in general athleticism.
Putting it all together
So, how long does it take to train for an Ironman?
In all the above examples, the time estimates I’m giving are based on someone training for each sport individually. If you’re only getting two or three sessions a week in for each sport, it will take much longer.
Ironman claim you can go from zero to Ironman in six months, but this is in probably a marketing technique as much as anything, as they want people to believe they can do it, so they’ll purchase an entry. It’s a delicate balance between making the event sound sufficiently impressive to make people feel like it would be a huge boast to finish, but accessible enough for them to enter.
It’s worth mentioning at this point that the DNF rates at Ironman events can be as high as 30%, although this can be as low as 5% in some events. This depends on some factors you’ll know ahead of time such as the course profile and climate, but inclement water and water conditions can make races which look easy on paper a true challenge. As an example, 70.3 Morro Bay in 2024 had a DNF rate of around 20% in the swim alone due to the water conditions, making for a 26.6% DNF rate in total.
I’m not trying to put you off entering an Ironman here, there’s nothing I’d love more than for you to sign up and start this fantastic journey, I just want you to go into this with your eyes wide open to the challenges it will provide, and the time it will require to train for the event. I don’t want you to spend several thousands on your race, only to have it all come crashing down around you as you didn’t give yourself enough time to prepare.
If you have a good level of base fitness and general athleticism you could well be ready in a matter of months, where for others it will be a multi year project just to make it round within the 17 hour cutoff.
If you’re in real doubt over your ability to finish, my recommendation is to make a 70.3 your target this year instead. The Ironman isn’t going anywhere, and I’d much rather you have a great experience training for both events rather than rush your way towards the full Ironman, have it completely dominate your life for a year only to end up failing to finish.
What I really want is for people to start this incredible health and fitness journey and develop habits which last a lifetime. I want you to be participating in endurance sport for decades to come, not get a reputation for always banging on about the one Ironman they finished twenty years ago. Building up to Ironman in a progressive fashion over time will not only make you much faster, it’ll also be more fulfilling in the long run.
