Looking at the Most and Least Likely World Records to Be Broken in Fukuoka


When it comes to predictions there are many a modality: you have can crystal balls, tea leaves, palm reading, and the list goes on. While it is unlikely that I’ll be able to read Regan Smith’s palm in the next week or see what Leon Marchand’s tea leaves say (if he drinks tea), one can use math to determine whose season-best times are closest to the world record. From those insights, one can make informed predictions.

If you want to see the hard numbers and the workings behind the math, scroll to the bottom of the article first and then come back up, but if you trust, or trust enough that I have some knowledge of swimming, then please read on.

To note, these are my educated predictions, and while they may overlap with several others, I did not poll the entire SwimSwam editorial board. Trying to get them to agree on a list would be like herding cats — just see the fantasy draft and the ribbing Ben received, or look at the 2023 U.S. Trial’s Pick’em Contest where I beat Yanyan and James on Day 1 but then ended up finishing 30+ points behind them. To be fair, I have placed top ten a few times, but that’s enough about me; onto the World Records.

Top 10 12 (I’m Indecisive)

Women’s 100 back

Despite Kaylee McKeown breaking the 200-back record earlier in March of this year and Regan Smith getting back under 2:04, I think the 100-back record is much more likely to fall. Personally, I think the 100 back is the most likely individual record to fall of all the events.  Not only was McKeown .05 off of the record at Australian Trials, but Regan Smith’s 57.71 is the fastest she has ever been in a lead-up to Worlds or the Olympics.

The event occurs on days 2 and 3, which is early in the meet and removes a higher possibility of illness or fatigue. As compared to the event below, this event is below 400m, meaning that there are two bites at the apple: a semi-final and a final. History shows that there are many world records from semi-finals; both of Adam Peaty’s long course records are from semi-finals, as is Sarah Sjostrom’s 50 free. Lastly, if there weren’t already enough opportunities, the lead-off legs in the medley relay can be used to break records (see Smith’s then WR of 57.57 from 2019), and both McKeown and Smith are projected to be swimming the backstroke in them.

Women’s 400 Free

Summer McIntosh
courtesy of Fabio Cetti

Having the three most recent world record holders in this event entered into the field certainly ups the likelihood of this event seeing a new world record. Summer McIntosh, who broke the record at the Canadian Trials with a time of 3:56.08, leads the entries over Ariarne Titmus’s 3:56.40 and Katie Ledecky’s 3:58.15. Like the 100 back, the 400 occurs early in the schedule, therefore, preventing fatigue from busy schedules and relay duties.

What puts the 100 back ahead of the 400 free is not only the more numerous opportunities to break the record in the back but also the much higher possibility that gamesmanship could come into play in the 400 free. While all three of them are high-caliber swimmers, they swim the 400 differently. McIntosh’s 200 split (1:55.91) was over a second faster than Titmus and Ledecky’s 200 splits (1:56.99 and 1:57.11) yet only finished ahead of their then-world record times by less than half a second (3:56.08 vs 3:56.40 and 3:56.46). As mentioned above, the hunt for the title (and bragging rights) may outweigh the hunt for the record. (Please feel free to disagree and comment about this point. I do think it is unlikely to happen, but stranger things have happened, and race strategy evolves all the time.)

Women’s 200 Back

While the 200 back does have a semi-final, due to it being longer and deeper in the schedule, a world record in the semi seems more unlikely than in the 100 back. Additionally, the 100 back is a more competitive field, with both Kylie Masse and Katharine Berkoff having entry times within a second of the world record. In contrast, in the 200, the 3rd seed Rhyan White’s entry time is 1.99 seconds off the record, meaning there is less pressure to swim fast in the semifinals.

That being said, McKeown swam 2:03.70 at Australian Trials with no competition (2nd place went to Jenna Forrester in 2:10.37), and with some pressure from an in-form Smith, McKeown could easily replicate her success from March. Smith, too, could have an inspired swim and take back her record after making a US International team in the 200 back for the first time since the 2019 record-setting season.

Men’s 200 Breast

Like the 400 free above, the 200 breast has seen the world record change hands often as of late. 5th seed Ippei Watanabe held it up to the 2019 Worlds, where Matthew Wilson took the record in 2:06.67. Since then, it has been broken twice, with the last and current record being held by Wilson’s compatriot Zac Stubblety-Cook. Stubblety-Cook’s 2:05.95 from last year represents the first swim under 2:06, but it may not be the last.

French phenom Leon Marchand swam the fastest time of this season, 2:06.59, against an empty field at French Nationals, and with ZSC’s back half and endurance, Marchand may be pushed to the gold and a new record, that is, if Stubblety-Cook doesn’t get there first. Questions have swirled as to if Marchand would swim this event at Worlds, but his presence on the entries list gives me hope. If, however, he scratches, this event sadly plunges down the list.

Men’s 100 Free

Photo by Con Chronis/Arenasport

Teenager, sprint phenom, a relative unknown until recently — one could be forgiven if they thought of David Popovici. Leading the charge this season (results from after Junior Worlds) is another teenager, China’s Pan Zhanle. Zhanle’s 47.22 from Chinese Nationals ranks him 11th amongst the top performers in the event, but he’ll have to contest with the #7 on the list, Kyle Chalmers, and of course, the fastest of all-time David Popovici. If the three are in form, I could easily see Popovici getting under the 46.86 he set at the European Championships last summer. Popovici followed up the 46.86 with a time of 47.13 at the Junior World Champs in Lima, which shows that his 46.86 wasn’t an outlier.

Men’s 400 IM

  • World Record – Michael Phelps, USA – 4:03.84 (2023)
  • Top Entrant – Leon Marchand, FRA – 4:04.28 (2022)
  • Fastest this Season – Leon Marchand, FRA –  4:07.80

Photo Andrea Staccioli / Deepbluemedia / Insidefoto

To head off the raucous comments about the 400 IM being more likely than the 200 breast, I’ll admit that it is a close call. Perhaps I am weighing the fact that Marchand was so close in the breast at Trials and not in the IM too heavily. Perhaps I’m placing too much belief in the power of Michael Phelps‘ last record. Maybe I’m not following the rationale I made about the 200 back regarding its placement in the schedule. Perhaps it is all three: the 400 IM seems more of a one-horse race than the women’s 200 back, and Phelps’ record deserves its reputation (it is the oldest in LCM).

Carson Foster had a great race at Trials this summer and looks to be in great form to help push Marchand. But coming in as the presumptive favorite and with the hype surrounding Marchand and this event in particular, I think we could see the oldest record on the books stay a little longer, but that is not to say I don’t think it’s not going to fall, it is just not as likely as others may think.

Other Possible Records to Fall:

  • Women’s 200 Free: One of only two super-suited records left on the books for the women is Federica Pellegrinis 200 free, 1:52.98, from the 2009 Rome meet. Leading this charge is Mollie O’Callaghan, whose 1:53.83 from the Australian Trials is less than a second away from Pellegrini. With pressure from compatriot Titmus, the multi-talented McIntosh, and Hong Kong’s Siobhan Haughey, this record could be under threat.
  • Women’s 800 Free: The lack of competition may hurt in this one, but if anyone can (and has already) shown their ability to swim to records alone, it is Katie Ledecky. She did it when she set the world record of 8:04.79 at the 2016 Rio Games. Her 8:07.07 from Trials is her third fastest time ever and is over 2 seconds faster than the time she swam at Trials last year. What may hold Ledecky back is the schedule: at US Trials, the 800 was before the 1500, while at Worlds, it will be the opposite. If she is close to the record in the 1500 or even under (one can hope), then the 800 would be all the more likely.
  • Men’s 200 IM: Based on what was swum last year at Worlds, this event could have the record broken by Marchand. He enters the meet with an entry time of 1:55.22 from last summer and a season-best of 1:55.68, showing he is much on form. Joining him atop the entry lists are Shaine Casas (1:55.24) and Wang Shun (1:55.55), who may give Marchand the push to break Ryan Lochte’s 1:54.00 world record from the 2011 World Championships, but with no one besides Michael Phelps having been under 1:55.00 its not likely.
  • Men’s 400 Free: Perhaps some wish fulfillment on my part, but I’d love to see another super-suited record fall. The current record holder is Germany’s Paul Biedermann, who swam 3:40.07 at the 2009 Rome World Championships.  Based on the math and form of swimmers this season, I think this event has a chance. Australia’s Sam Short leads the way with the top time this season, 3:42.46, while his teammate, Elijah Winnington, is the top seed with a time of 3:41.22. If the two of them and other potential gold medalists like Lukas Märtens can just race and not get bogged down in strategy, then I think there is a chance.
  • Men’s 100 Back: I am very much on the fence with this one. Sometimes I feel enthusiastic about the record being broken and other times, not so much.  In the semi-finals last summer, Apostolos Christou set a Greek record of 52.09 (also a championships record) and Thomas Ceccon set an Italian record of 52.12. When the finals came around, Ceccon dropped a further half a second to set the current record of 51.60, while the American contingent dropped under 52 as well to grab 2nd and 3rd. This year both Ceccon and Ryan Murphy have been faster than they were in the lead-up to last year’s meet, so both could push each other to break the record, but both would need to replicate their massive drops from the semi-finals to finals.
  • Women’s 100 Fly: In my initial compiling of records, I downplayed the likelihood of this one being broken. Perhaps I ignored the flaws in my math (see under Disclaimers), or perhaps I didn’t look back far enough, or perhaps I just overestimated how dominant Sjostrom’s 55,48 record is, but I am big enough to admit my mistakes. Torri Huske‘s Trials time is faster than it was last year when she went on to swim 55.64.  Maggie MacNeil is a little off where she was in the lead-up to the Olympics, where she swam 55.59, but hasn’t needed to taper. If you add in last year’s bronze medalist Zhang Yufei and Australia’s Emma McKeon, who both have been sub-56, this record could be gone.

Not Happening, or I’ll Eat My Hat

  • Women’s 200 Breast: Lacking the recent world record holder will always hurt the chances of seeing a record broken, especially if that record was set this year. Russia’s Evgeniia Chikunova swam 2:17.55 in April of this year.  The previous world record holder, Tatjana Schoenmaker, has a best time that is 1.4 seconds away and with no entry times within 3 seconds of the WR (top seed Lilly King’s 2:20.95 being the closest), this just further cements this as being an unbreakable record, as least for this meet.
  • Women’s 50 Fly: Equally as untouchable records is Sarah Sjostrom’s 50 fly record of 24.43. A record that was notably swum outdoors, a topic that was recently brought up about hypothetically keeping separate indoor and outdoor records. While Sjostrom has been under 25 seconds this season, no one else ever has.
  • Women’s 200 Fly: Liu Zige’s 2:01.81 is from the 2009 Chinese National Games and, besides Pellegrini’s 200 free is the only other remaining super-suited record on the books for the women. The 200 fly looks to be a great race between Smith and McIntosh, but I just don’t see a swim under 2:02 likely, nor under 2:02.50 for that matter. (I initially wrote 2:03 but am hedging my bets)
  • Men’s 200 Back: There’s a reason why half of the remaining super-suited records are at the 200 distance. The suits allowed for maximum compression to be used while maintaining buoyancy and limiting friction. Aaron Peirsol’s 200-back record of 1:51.92 is the furthest away(percentage-wise)  in both the men’s and women’s analyses. Set in 2009 at the Rome World Championships, Peirsol’s 1:51.92 is a way ahead of Ryan Murphy’s season-leading time of 1:55.03 and is still a full second and a half faster than Murphy’s best time of 1:53.57
  • Men’s 50 Fly: While not a super-suited record, Andriy Govorovs 22.27 will still be challenging to break this season as all three of last year’s medalists are not returning and the fastest time this season belongs to Oleg Kostin (22.62), who is ineligible to compete. The swimmer with the fastest in-season time is Ceccon, who, in addition to being known more as a backstroke, is more than half a second away.
  • Men’s 100 Breast: Adam Peaty remains the only swimmer to have broken 57, swimming 56.88 in the semifinals of the 2019 World Championships. Peaty also holds 19 of the top 20 times, with #20 being Arno Kamminga’s 57.90. Qin Haiyang’s leads the world rankings and the entry lists with 57.93, the only time under 58 on lists, but this year’s 100 breast, especially without an in-form Peaty, will be much more about the placing, not the time.

The Boring Math Part

The tables below show on the left side the world record holder, their time, and the year it was set. The right side shows the fastest swimmer this season and their time. The furthest right column shows what percentage the fastest time comprises of the world record. The table is sorted from highest to lowest, with 100 meaning the fastest time this season equals the world record. Any yellow highlighted squares denote that these swimmers have the fastest times among entered swimmers and any red squares indicate super-suited world records. From this one can deduce several things, including:

  • Several super-suited records could fall (records set in 2008-2009).
  • The women’s backstrokes events seem to be the stroke most under threat.
  • For the men, no one stroke stands out more than the others, but fly seems the least likely.
  • Just because the current world record holder is entered in the event, it doesn’t mean that it is close to being broken (see Sjostrom’s or Govorov’s 50 fly).

The Closest Based on Math Alone

Using just the percentages calculated, one would assume that the three world records that were broken already this year would be the most likely to be rebroken, yet when taken into context, this is not the case.

While Summer McIntosh and Kaylee McKeown should definitely be in form to challenge their world-record swims (McIntosh in the 400s of free and IM and McKeown in the 200 back) from earlier this season, they may not have to do so.

The 400 free looks to be a barn burner of an event between McIntosh, Katie Ledecky, and Ariarne Titmus, and while the record could easily be broken, the trio might also focus on the gold and not the record. The same argument can be made for the 200 back as McKeown and her chief rival Regan Smith may focus on the win instead of the record. (see above)

In the women’s 400 IM, McIntosh (or someone else) could win gold in a time under 4:31 (4:32.04 was the gold medal-winning time in 2022) and not have to approach her world record mark. Her world record mark of 4:25.87 was set at Canadian Trials, where she had no real competition and therefore did not have to worry about being overtaken should she have tightened up at the end.

Florian Wellbrock courtesy of Fabio Cetti

The same can be said for the men’s 1500, where percentage-wise, the closest to breaking the record so far this year is Florian Wellbrock. The German swam 14:34.89 back in April at the 2023 Berlin Open and while still over 3 seconds off Sun Yang’s world record of 14:31.02, over the course of 1500 meters, that difference equates to just .13 of a second per 50, but like in the women’s 400 IM, Wellbrock had very little competition so if he had started to fade, the consequences were minor.

At Worlds, the consequences are far from minor, however. Over 1500 meters, the competitions and gamesmanship being played may turn the focus more towards the gold than the record. For example, Gregorio Paltrinieri last summer played the field to his advantage, but if he had hit a wall at the 1400m mark after going out so fast or if he failed to qualify (remember he was 7th coming into the final, just 3 seconds off of not returning) then it would be a very different story.

The other men’s events at the top of the list, the 200 breast and 100 free, are intriguing options. (see above).

Disclaimers Regarding the Math

Please note that there are several flaws in this math, which is why it is not used as the sole predictor. It provides a framework off of which to help make educated predictions. Those flaws include:

  • Not every swimmer has had to taper or even compete to make their country’s Worlds Roster. If they were pre-selected, then they might not have had to swim rested yet, therefore, skewing the results slightly.
  • We used season best times, not entry times.
    • Using entry times might have led to some changes in the percentages. For example,  Marchand would be much closer in the IMs.
    • Entry times, however, can overlook one’s current form. Several swimmers are entered with times from last season that they have not yet been close to replicating.
  • We also only included individual events due to the complex nature of relay rosters and the increased opportunities for disqualification.
  • Faster events are slightly skewed towards the bottom. As records approach zero, differences in times make larger differences, i.e., the men’s 50 breast and 50 fly. Ceccon is closer to Govorov’s record than Sun is to Peaty’s, but because the fly record is faster than the breast, the math plays out that Sun is “closer as a percentage.”

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10 months ago

Without Kristoff Milak the 200 fly is completely out of reach

10 months ago

I am just surprised how you could think that there is any chance that someone could beat Milak’s 200 fly record…

11 months ago

Surprised no mention of the Women’s 200IM. Even with Summer out, it very well could still happen.

Bobo Gigi
11 months ago

Hi everyone.
I don’t follow swimming as closely as a few years ago but based on the things I’ve watched this season here are my few thoughts about worlds. In no particular order.

It’s the summer of Summer. The young Canadian is ready to take over the world.
400 IM easy win with a new world record if she’s not too tired on the last day of the meet.
400 free. It will be close with Ariarne Titmus. The youth should prevail.
200 fly. It will be a great fight with Regan Smith but she’s very likely to win the gold.
200 free. I’m surprised she chose that event over the 200 IM where she… Read more »

Reply to  Bobo Gigi
11 months ago

Welcome back Bobo

Reply to  Bobo Gigi
11 months ago

return of the king

Reply to  Bobo Gigi
10 months ago

Great to see you Bobo, and I didn’t mind the long post, all well-said!
I have to say I hope Léon is just short of the WR in Fukuoka so he can smash it on the first night of swimming in Paris next year. Would be absolutely legendary. Hollywood indeed. But I know of course he and Bob have their sights on that record this week.

Reply to  Bobo Gigi
10 months ago

Quick someone make the showing up to a fancy occasion in regular clothes vs showing up to bobo’s return in a suit meme. The legend has returned and I agree with a lot of what you’re saying.

Last edited 10 months ago by PFA
Reply to  Bobo Gigi
10 months ago

bobo you’re a swimswam legend

we’re all thrilled to see you again!

Paul Thomas
11 months ago

The women’s 200 fly record looks literally unbreakable to me. The men’s 800 free record is going to require someone with Ledecky’s speed and stamina, but with testosterone, which is to say it requires a person who does not currently exist on Earth.

The men’s 200 back record should be reachable… someday. The biggest problem with that race is that AQUA keeps scheduling it at times that conflict with the schedules of the kind of Phelps/Lochte-like swimmers who would be most likely to break it. At least in 2024 it’s just a finals-semis overlap rather than a finals-finals conflict as existed for so many years.

Last edited 11 months ago by Paul Thomas
11 months ago

Men’s 800 is the least likely by far.

11 months ago

mens 50back clearly has a great shot… youve got the top 2 performers ever competing at their best.

11 months ago

Piersol’s 2 back record is ridiculous and it looks even crazier with the laughably weak international 2 back fields.

Obviously 800 free is up there too and I don’t think anyone is touching Govorov’s 50 fly for another 5+ years