About the data

iRun42 collects key facts about half marathons, marathons and ultras worldwide, on road and trail, so you can find a race that fits: flat or hilly, cool or warm, close to home or a bucket-list trip.

Where the numbers come from

• Race details (dates, elevation gain, entry type, fees, field size, records) are curated by hand from published race information. They are approximate. Fees are rough USD equivalents of a standard entry.
• Dates marked “est.” are inferred from the race’s usual place in the calendar. Always confirm on the official site before booking travel.
• Weather is computed from 10 years (2016–2025) of hourly ERA5 reanalysis data via Open-Meteo. For each race we sample the race day ±3 days, from the start time for 5 hours. It describes typical conditions, not a forecast.
• Course maps and elevation profiles are available for a subset of races. Routes are approximate and trace the shape of the course. Profiles are sampled from 90m terrain data along that route.
• Maps © OpenStreetMap contributors.

How the site is funded

Some links to hotels, flights, activities and gear are affiliate links: if you book or buy through them we may earn a commission, at no extra cost to you. Banners and races marked “Sponsored” or “Featured” are paid placements. Payments never change the race data.

Your data

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