Boston 2027 Registration: Dates and Timeline

Published July 25, 2026 · Estimates, updated each registration cycle

Short answer: Qualifier Registration for the 2027 Boston Marathon runs for five days, from Monday, September 14 through 5:00 p.m. ET on Friday, September 18, 2026. The Boston Athletic Association confirmed the calendar in its July 22, 2026 announcement, and every qualifier applies in that same window. Applying on day one does not help, because acceptance is decided by your buffer, not by the order in which people apply.

The confirmed 2027 timeline

Here is the sequence the BAA has laid out for the 131st Boston Marathon, which is scheduled for Patriots' Day, Monday, April 19, 2027:

• Qualifying window: opened September 13, 2025, the day after the 2026 Registration Week closed, and runs until the 2027 application window. Any certified marathon in that window can supply your qualifying time.
• Registration Week: September 14 through September 18, 2026. Five days, closing at 5:00 p.m. ET on the Friday. Submit any time inside that window; there is no first come, first served advantage.
• Downhill adjustment applied: during that same week, times run on courses with a net elevation drop greater than 1,500 feet are index-adjusted for the first time (see the downhill rule explainer).
• Cutoff and random selection decided: after the window closes, the BAA fills the field from the fastest buffers down, sets the cutoff, and then draws about 1,000 more from the qualifiers who fell just short (see the new qualifier selection).
• Notification: all applicants learn of acceptance or non-acceptance by early October 2026.

What is genuinely new for 2027

Two things separate this cycle from past years. First, the downhill index means a steep net-downhill qualifier is treated as slightly slower than the clock during that Registration Week, so a borderline time can shift. Second, missing the cutoff is no longer an automatic no: roughly 1,000 runners below the line are pulled in at random. Neither changes the core process, and neither changes the deadline. If your application is not in by 5:00 p.m. ET on September 18, none of it applies to you.

How acceptance is decided inside that week

Once the window closes, the BAA ranks applicants in each age and gender group by how far under their standard they finished, then accepts from the fastest buffers down until the roughly 30,000 field is full. The slowest buffer that still gets in becomes that year's cutoff. For reference, the 2026 race cut at 4:34 under the standard, and our central estimate for 2027 is about 5:15, which is an estimate and not a BAA figure. Whether your buffer clears that line is the whole game, so it pays to know your number before September (see how much buffer 2027 is likely to need).

What to do before Registration Week

Three things make the September window painless. Verify your qualifying time early so the application is a short form rather than a scramble (see pre-verification). Confirm your race was a certified course and check its net drop if it was a downhill race. And know your buffer: run your finish time and age through the predictor to see how far under the standard you are, your rough odds of clearing the estimated cutoff, and whether that buffer would have been accepted in each of the last thirteen cycles. Do that now and Registration Week is a formality, not a gamble.