What is the estimated course effect?

How much faster or slower a course plays than a neutral benchmark — the Compass Neutral Course, a flat, cool, sea-level reference with 250 ft of climbing and a 45°F/35°F-dew morning. It combines the exact BAA downhill adjustment with two estimates: a terrain cost/credit and a typical-weather heat cost. Because the terrain estimates vary by runner, we show a range and a confidence level rather than a single exact time.

How reliable is the estimate?

The BAA adjustment is exact under the published rules. The terrain and weather components are heuristics we have not yet validated against real runner results, so we present a plausible range and mark confidence as moderate or low. Treat it as a way to compare courses, not a prediction of your finish time.

What do the downhill bands mean?

Among penalty-free courses (under the BAA's 1,500 ft net-descent line), we split the descent into gentle (200–599 ft), moderate (600–999 ft), and aggressive (1,000–1,499 ft). A 250 ft drop and a 1,450 ft drop are very different races, so we don't lump them into one 'sweet spot'. At 1,500 ft or more, the BAA adjustment applies.

Do steep downhill marathons still count for Boston?

Up to a point. Under the rules for the 2027 qualifying window, 1,500–2,999 ft of net descent adds 5:00 to your time, 3,000–5,999 ft adds 10:00, and courses dropping 6,000 ft or more are not accepted at all.

The instrument

BQ Course Finder

A Boston Qualifier isn't judged on your clock time alone: the BAA adds a downhill adjustment on steep point-to-point courses, the profile shapes how fast you run in the first place, and typical race-morning weather taxes everything. We combine all three into an estimated course effect — how much faster or slower a course plays versus the Compass Neutral Course (a flat, cool sea-level course (250 ft climb, 45°F / 35°F dew)) — for every Boston-qualifying marathon in the catalog. The BAA adjustment is exact; the terrain and weather effects are estimates, so each race shows a range, not a false-precise number.

All BQ courses (26)Downhill sweet spot (5)

Frequently asked

What is the estimated course effect?: How much faster or slower a course plays than a neutral benchmark — the Compass Neutral Course, a flat, cool, sea-level reference with 250 ft of climbing and a 45°F/35°F-dew morning. It combines the exact BAA downhill adjustment with two estimates: a terrain cost/credit and a typical-weather heat cost. Because the terrain estimates vary by runner, we show a range and a confidence level rather than a single exact time.
How reliable is the estimate?: The BAA adjustment is exact under the published rules. The terrain and weather components are heuristics we have not yet validated against real runner results, so we present a plausible range and mark confidence as moderate or low. Treat it as a way to compare courses, not a prediction of your finish time.
What do the downhill bands mean?: Among penalty-free courses (under the BAA's 1,500 ft net-descent line), we split the descent into gentle (200–599 ft), moderate (600–999 ft), and aggressive (1,000–1,499 ft). A 250 ft drop and a 1,450 ft drop are very different races, so we don't lump them into one 'sweet spot'. At 1,500 ft or more, the BAA adjustment applies.
Do steep downhill marathons still count for Boston?: Up to a point. Under the rules for the 2027 qualifying window, 1,500–2,999 ft of net descent adds 5:00 to your time, 3,000–5,999 ft adds 10:00, and courses dropping 6,000 ft or more are not accepted at all.

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How this is computed: the BAA adjustment is exact under the 2027-window downhill rules (verified July 2026); the rest is an estimate. The baseline is the Compass Neutral Course: a flat, cool sea-level course (250 ft climb, 45°F / 35°F dew). Climb cost uses the coaching rule of thumb of ~1.5 s per foot of gain over the full distance; net-descent assist starts at 0.55 s/ft and decays through the BAA's own bands, since eccentric quad fatigue claws back free speed on steeper drops. Both are unvalidated heuristics, so we show a ±35% range and mark confidence. The heat penalty applies our temp + dew point chart to each race's start-line climatology, priced against a 3:30 reference finish. Ranges compare courses; they are not a prediction of your finish. See the methodology page for provenance.