Marathon Course Converter
Course speeds estimated from 17 million finishes on 1,000+ marathon courses, holding the runner, the year, age, and weather constant. Look up how fast a course really is, or convert your time from one course to another.
How fast is your course?
Distribution of course speeds relative to Boston (0%). Negative = faster course. Minutes shown elsewhere are scaled to a 3:20 finisher.
Convert your time between courses
Ranges are measured from millions of runners who raced again within 18 months — they mostly reflect how much runners vary (fitness, race execution, weather), not uncertainty about the courses: repeat performances by the same runner on the same course vary nearly this much. The range is asymmetric because a bad marathon loses more time than a great one gains.
The same performance at other ages
Equivalent finish times for this performance at across ages, from the estimated age–gender curve.
How this works
Every estimate comes from a statistical model fit to 17 million marathon results (2000–2026): each finish is decomposed into a runner’s ability, the course, the year, an age–gender curve, and race-day weather. A course’s speed is how much faster or slower the same runner runs on it compared to the Boston Marathon. Conversions cancel out the runner entirely — only the course gap and the age curve are applied to your time, at neutral weather.
Point estimates of course speed are precise (typical standard error under 1%). The prediction ranges are honest about something different: how much any runner’s next marathon varies. That spread is real — the same runner repeating the same course a year later varies nearly as much — and it is skewed slow (blow-ups happen; miracle days mostly don’t).
This is a companion tool to an academic paper on marathon course speed and Boston qualifying. Course effects are population averages and not a guarantee of individual results.