Ironman: How Slow Can You Go?

One of my biggest fears when I was training for my first Ironman triathlon last year was that I might not finish.  Initially that I wouldn’t make the bike cutoff, but then potentially with the run depending on how things had gone thus far. So exactly how slow can you complete an Ironman without getting disqualified?

So I actually mapped it out, and I want to share the information! Each race is a little different in terms of its cutoff times, so use this as a guide but check your Athlete Guide for more specifics as to your race.  I was looking at Ironman Louisville and Ironman Wisconsin guides when I wrote this.  For your race, please check the most up-to-date Athlete Guide on the race website.


Ironman- How Slow Can You Go?


You have to swim 2.4 miles in 2 hours and 20 minutes.   This translates to a 3:37/ 100m pace. If you swim in a yards pool, then your slowest 100 pace is going to be 3:18/100yd.

Swimming for 2:20 will get you out of the water at 9:20 AM (assuming a 7 AM start, the standard at most Ironmans).

Katrina & I

Katrina & I


Let’s just assume a 9 AM start.  You have to be at 60 miles by 2:45 PM  —> this translates into a 10.43 mph pace.

If you have to hit 112 miles by 6:20 PM,  then you need to ride at an overall 12 mph.   If you have to complete 112 mi by 5:30 pm, that’s an overall 13.1 mph bike pace.

If you took your whole 2 hours and 20 minutes on the swim, and don’t get onto the bike until 9:30 AM (you got out of the water at 9:20 and then took 10 minutes in transition to get to the bike), then you have the following times:

  • Get to the 60 mile cut-off by 2:45 PM –> you need to ride at 11.43 mph for the 5.25 hours
  • Go the full 112 miles and arrive back by 5:30 PM –> you need to ride at 14 mph for the 8 hours
  • Go the full 112 miles and arrive back by 6:20 PM –> you need to ride at 12.67 mph for the 8 hours, 50 minutes



Assuming a 6:30 PM start onto the run course, and a requirement to pass the 13.1 mile mark by 9:45 PM, you’d have to run at a 14:53 min / mi pace to complete that 13.1 miles.  To get to  26.2 by midnight (having started at 6:30 pm), you need to run an overall 12:35  min/mile pace.

Half Way Point 70.3 Lauren Runs


My goal in this is not to scare anyone, but to put the paces/speeds out there for the bare minimums.  These are assuming you are taking all of your time on each of the disciplines.

What should I do?

Gather up your training paces, or benchmark tests.  Be honest with yourself about the Ironman and where you are in training:

  • What was the speed of your average long ride?
  • What about your average long run?
  • What’s your average swim pace?
  • What sport are you most nervous about?

Play out the scenario with your conservative paces — remember what you do in training is likely what you’ll do on Ironman race day.  So for me last year, I predicted a more realistic timeline that I was able to share with friends and family of what I thought I’d do.  This helped my fan club with knowing when they might expect to see me.  I shared with them all of the scenarios so that they’d have that information.

Just how slow can you go in an @IronmanTri ? Figure out if you'll finish in time! #Triathlon Click To Tweet

Some calculators you can use once you get your benchmark paces:

I took my paces and turned them into estimated times: 

Swim:  2:10/ 100m —> 1:23:41
T1:  10 minutes
Bike:    14.5 mph —> 7:43 15.5 mph —> 7:13 16 mph —> 7:00:00
T2:  10 minutes
Run:  12:30 —> 5:27 total.

I then translated those estimated times into “Time of Day” predictions that I could share with my family and friends to help with them spectating – both at the race and virtually:

7:30 AM Start:
Swim out/Bike Out:  9:33 AM
Bike In:  4:33 PM (16 mph)
Run Out:  4:43 PM
Finish:  10:15 PM.

While that didn’t happen (unexpected things always come up on race day!), this did give everyone involved with race day a better idea of what was going to happen when!  I periodically did my check-in on paces starting a few months out (hey, I’m a planner), and then shared with my family & friends a week or two before IMLOU.

I hope you found this informative and helpful!  

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  1. This is really interesting! I know several people who have started Ironmans and not finished for various reasons but I wonder if they did these types of calculations beforehand.

    I still can’t fathom swimming 2.4 miles, though, so I don’t see an Ironman on my horizon 🙂
    Erin recently posted…The Stanley Cup Goes to WorkMy Profile

    • Yeah – I like doing these and knowing “I would finish” even if it’s not super fast. BTW – you have a great time for your sprint swim— you’d rock ironman swimming!

  2. This is actually really helpful! I’ve done this a ton of times for my HIM times and I know that I will do it eventually for when I do a full as well. It all sounds like it’s not too bad until you realize it’s one after the other!
    Tiina recently posted…Wordless WednesdayMy Profile

    • Yeah – I’d want to make sure that I wasn’t at risk for not making the pace on every single sport. I think that’d be mentally incredibly challenging but if you have these paces in mind (esp for swim & run), it’s pretty straightforward to figure out whether you might be ready to do an ironman based on your endurance paces.

  3. I did something very similar for Ironman WI last year. I had a very detailed email of the approximate time frames for when I would be done with the swim, what time I would be done biking, etc. I actually went faster than I expected but I didn’t want to be too optimistic in my timeline. I also had pictures of what I was going to be wearing 🙂 so my spectators would spot me!
    Alyssa recently posted…Five Things FridayMy Profile

  4. I’m looking at doing my first full next fall (possibly Louisville because it’s been moved to October), and this actually makes me feel so much better about considering racing a full! This makes it seem much more doable, since my biggest fear would be to DNF.

  5. Great post! I admire you so much! I’m 53 and while I can’t swim well, nor can I run anymore (some partially calcified tendons in the lower leg and feet), I love my cycling these days, about 80/wk on average for the year, and up to 200mi/wk during normal biking weather. The look on your face in your pictures is one of infectious enthusiasm, something that rubs off on me quite easily. I’ll probably never do an IM nor a Triathlon because of the swimming and running problems, but your post is inspiring. Thanks for sharing your experiences!

    I am a hill (driftless region) and climbing enthusiast, and reading your accounts has clarified what I should be shooting for as a reasonable average speed. Notably, the IM route in Madison WI has about the same elevation gain that I’d expect to do in 65 or 70 miles, so it look very doable. [Mind you, put swimming in front of that, and running right after, and it looks downright…challenging! That’s why I said that I admire you!]

  6. I loved reading your article! My sister and I have been running marathons for several years, and we grew up doing swim team for about 10 years. We declared a couple days ago that we’d like to train for an iron man so we’ve begun our “pre-training” which is just us trying to bike and swim in addition to running. We intend to start with a sprint tri then build on the distance until we build up enough tri experience for an ironman, so we hope to do one in two years. What advice would you give to us in terms of training and prepping? The idea of doing one sounds both incredibly exciting and incredibly frightening haha. And are their any races in particular that you would recommend?

    • Hi Kate, Congratulations on taking the plunge into triathlon! Check out my Triathlon 101 page for more posts on the various aspects of triathlon. I’d definitely recommend getting a sprint and an olympic distance race under your belt before registering for your Ironman event. Ironman is a big commitment, and it’s good to make sure that you’re going to enjoy training before you commit to it!

      It’s totally OK to be frightened by prospect of doing an Ironman, the good part is you also have the excitement! My other big tip for you would be to try and find a group of people who also do triathlons that you can get involved with. Whether it’s just other people you know, a social club, or a formal training group, I find that having other people to commiserate with, learn from, and spend my time training with is beneficial. And that way you’re getting some social time in too while training and racing!

      Feel free to email me at laurenrunschicago-at-gmail-dot-com if you have any other questions! I’m happy to help you get going with training and on your way to your first triathlon!