What Do the Results of the 2025 London Marathon Mean for the 2026 Boston Cutoff?

It’s been a crazy couple of weeks for the Boston Marathon cutoff time.

At the end of March, the projected cutoff time was around 5:20. Although the trend towards larger fields had continued – the number of qualifiers was still dropping slightly, moderating the cutoff time projection.

Then along came Boston. Although I anticipated there being more qualifiers at Boston this year than last year, the swing was larger than I expected – and the projected cutoff shot up to 6:44. This was on top of strong results from REVEL Mt. Charleston and Jersey City, which both contributed additional qualifiers.

The last major race to take place this qualifying period was the London Marathon. I uploaded the results to the tracker yesterday, and it caused a significant enough swing in the projection that I thought it warranted some discussion.

So let’s take a look at what happened this weekend – at London and in the other races.

Results of the 2025 London Marathon

Here’s the short version: the number of qualifiers at this year’s London Marathon dropped 30% compared to last year.

Last year, there were 8,894 qualifiers – and this year that dropped to 6,185. That’s a lot.

In part, this is likely due to the weather. The weather was warmer than usual, with temperatures rising into the high 60’s late in the day. The earlier waves who finished first were likely less impacted, but I’m sure the back of the pack struggled as time went on.

If you were to judge this just based on the times of the elites, you would have thought it was a perfect day. Tigst Assefa set a new course record for the women’s only marathon – only 25 seconds off Paula Radcliffe’s mixed-gender record of 2:15:25. And Sabastian Sawe ran the second fastest time in London history, behind only Kelvin Kiptum’s 2023 2:01:25.

But the mass field was definitely slower than last year. If you were to apply last year’s Boston qualifying times to this year’s field – to make an apples to apples comparison – last year saw 16.5% of runners qualify and this year the number was 13%.

The visual above puts this in perspective by showing the number of BQs at London since 2019.

Although this year’s number – the blue bar – is lower than the last two years, it’s actually more than there were in every other previous year. The red section of the final bar shows the number of runners who would have BQ’d under the old times (1,198), but missed the mark this year.

So although it was warm, the weather didn’t decimate the field. A significant factor in the drop in the number of qualifiers was simply the tougher qualifying times.

Looking under the surface, the field also shifted slightly – by about 2 percentage points – towards runners under 40. They have the toughest qualifying times compared to the rest of the field, so this also played a part in the lower numbers.

What About the Other Races?

Although London was the biggest race of the weekend, there were a number of others that took place. I added fourteen other races to the tracker this week.

Four of them saw double digit growth – Eugene, Oklahoma City, Salt Lake City, and Illinois. A few races saw declines in the number of finishers, but overall this full slate of races grew by almost 10%.

In terms of qualifiers, Glass City was the big mover. It’s much smaller than London, so it doesn’t “matter” much in the scheme of things. But the number of qualifiers there jumped from 206 last year to 307 this year. Any other week, this would have been big news.

The interesting thing here is that Glass City had fewer finishers this year. The weather was much better this year, so that likely played a part. I also wonder if some of the runners displaced by the cancellation of Carmel ended up here – putting a larger than usual number of possible BQs into the field.

Across the board, there were some races with more qualifiers and some with fewer. Add them all up, and they basically cancel each other out and yield a neutral amount of qualifiers vis-a-vis last year. Almost as if they hadn’t implemented new qualifying times.

So if you set aside London, the results from this week would have continued to push the cutoff time up.

So What’s the Net Impact for Now?

With all of these results incorporated into the tracker, the projected cutoff time is 5:53.

So it’s back down from its peak of 6:44. But it’s also well above what it was just a few weeks ago.

In between the wild swings caused by Boston and London, the remaining races in April have a) continued to grow and b) yielded similar amounts of qualifiers compared to last year. That’s nudging the cutoff time higher and solidifying the earlier trends suggesting a 5:00+ cutoff time.

It’s also worth keeping in mind that of the two races, Boston is more consequential than London.

They both had large swings in qualifiers, but far more Boston runners turn around and run Boston again. Last year, 18.5% of the qualifiers at Boston ended up running again. Only 12.4% of the qualifiers from London ran Boston this year. If you assume those same rates this year, the two races will combine for an extra 200 or so applicants.

At the end of the day, this month definitely pushed the projection up – and it likely cemented a cutoff time above 5:00.

What Can Still Change?

In terms of results, we’re just about to the end of the road.

When you count up all of the finishers in the qualifying period last year, we’ve now completed races covering 85% of those finishes. There’s a lot of inertia to the current projection, and there simply aren’t enough results left to sway things much in either direction.

There are a couple large, fast races to go – notably Grandma’s and Ottawa. But most of the other large races are hilly and don’t produce a lot of qualifiers.

The biggest remaining variable is – how many of the current qualifiers have run more than one qualifying race this year?

I’m going to update the tracker to identify (to the extent that it’s possible) unique runners and only use their best time for the calculations. This will weed out some duplicates.

That doesn’t necessarily mean that the projection will go down, though. The same methodology is currently applied to both qualifying periods.