Which Qualifying Time Should You Submit?

Published September 3, 2026 · Estimates, updated each registration cycle

Short answer: submit the time that leaves the biggest buffer after the Boston Athletic Association's adjustments, which for the 2027 race is not always the fastest number on your watch. For most runners the fastest qualifier is still the right answer, and the application form makes that easy. But 2027 adds a rule that can flip the order of two of your own races, and Registration Week runs September 14 through 18, 2026, so it is worth ten minutes now rather than a guess on the day.

Why the fastest time usually wins

Your qualifying standard does not depend on which race you submit. It is set by your age on race day, April 19, 2027, and your gender, and it is the same number no matter whether you submit a marathon from last October or one from this spring. That matters, because a lot of runners assume that a birthday between their two qualifiers changes the comparison. It does not (see how Boston age groups work). Both races are measured against one standard, so the faster finish produces the larger buffer, and the larger buffer is what the ranking uses.

That is the whole selection mechanism in one sentence: the BAA sorts verified applicants by how far under their standard they finished and fills the field from the fastest buffers down. Whatever buffer the field runs out at becomes the cutoff, currently expected to land near 5:15 for 2027.

The 2027 exception: the time index

For the first time, the BAA is applying time index adjustments to qualifying times run on courses with more than 1,500 feet of net elevation drop. A time from one of those races is assessed as slightly slower than the clock showed. The BAA has not published the exact arithmetic, which is precisely why this decision needs care.

The practical consequence: if your fastest race was a steep point to point downhill and your second fastest was flat, the gap between them can close, and in a narrow case it can reverse. A 3:02:10 from a heavily dropping course and a 3:03:30 from a flat certified marathon are 80 seconds apart on paper and may be much closer once the index is applied. If the two times are within a couple of minutes and only one of them came off a big drop, the flat one is the safer application. Our explainer on the downhill adjustment and the list of affected races cover which courses cross the threshold.

Three other reasons your fastest time may not be the one

• It is outside the window. A personal best from two years ago is worth nothing if it falls before the qualifying window opens. Only races inside the window count (see the qualifying window).
• The course is not certified. A fast time on an uncertified course is not an eligible qualifier, regardless of the finish clock.
• The result cannot be verified. The BAA checks your submission against the official published results of that race. If a small event has taken its results offline or listed you under a misspelled name or the wrong age, that time is a liability. A slightly slower race with clean, findable results is the better application.

How to make the call

Write down every eligible marathon you finished inside the window with its official time and its net elevation drop. Run each one through the cutoff predictor with your race day age, and note the buffer and the odds it reports. If one race is clearly fastest and it was flat or rolling, submit it and stop thinking about it. If the fastest one came off a steep drop and another candidate is within about two minutes, submit the flat one. The tool does not model the index yet, so treat the odds on a steeply downhill time as optimistic.

One thing you do not need to worry about is timing. Registration is not first come, first served, and every application filed before 5:00 p.m. Eastern on Friday, September 18 gets equal consideration. Use the extra days to pick the right time rather than the first one.