A standard marathon is exactly 26.219 miles (42.195 kilometers). This distance is the international benchmark for long-distance road running events, requiring significant endurance, specific training, and strategic pacing to complete successfully while maintaining your target speed.
The marathon distance isn’t a clean, round number by accident of math — it’s the product of royal convenience. At the 1908 London Olympics, the marathon course was originally planned to cover roughly 25 miles, starting at Windsor Castle and finishing at White City Stadium. But organizers extended the course so it would start on the lawn of Windsor Castle (so the royal children could watch the start from their window) and finish directly in front of the royal viewing box inside the stadium.
That extension pushed the total distance to 26 miles and 385 yards. The number stuck, and in 1921 it was formally standardized as the official marathon distance by what’s now World Athletics — meaning every certified marathon course in the world today, from Boston to Chicago to your local hometown race, measures exactly 26.2 miles.
| Unit | Distance |
|---|---|
| Miles | 26.2 miles |
| Exact miles/yards | 26 miles, 385 yards |
| Kilometers | 42.195 km |
| Meters | 42,195 meters |
| Feet | 138,435 feet |
| Race | Distance (Miles) | Distance (KM) |
|---|---|---|
| 5K | 3.1 miles | 5 km |
| 10K | 6.2 miles | 10 km |
| Half Marathon | 13.1 miles | 21.1 km |
| Marathon | 26.2 miles | 42.195 km |
| 50K Ultramarathon | 31.1 miles | 50 km |
| 100 Mile Ultramarathon | 100 miles | 160.9 km |
Notice the marathon is exactly double the half marathon distance — which is why so many training plans use the half marathon as a benchmark checkpoint partway through marathon training.
If you’ve ever finished a marathon and your GPS watch read something like 26.4 or 26.6 miles, that’s not a measurement error in the course — it’s almost always caused by the way GPS watches calculate distance versus how a certified course is actually measured. Certified courses are measured along the shortest possible racing line (called the “tangent”), while runners rarely run that exact line perfectly, especially around turns and aid stations — meaning your watch often reads slightly longer than the official distance even on a properly certified course.
The name itself predates the 26.2-mile distance by over 2,000 years. It comes from the legend of a Greek soldier who supposedly ran from the town of Marathon to Athens to deliver news of a military victory, then collapsed. When the modern Olympics were revived in 1896, organizers created a race to commemorate that legend — though the original 1896 Olympic marathon was actually closer to 24.85 miles, not 26.2. The now-standard 26.2 mile distance wasn’t locked in until that 1908 London Olympics course extension.
Is every marathon exactly 26.2 miles?
Yes — any marathon seeking official certification (required for results to count toward rankings, records, or Boston Qualifying times) must measure exactly 26.2 miles / 42.195 km along a certified course.
Why is a marathon 26.2 miles instead of a round 26 or 25 miles?
The extra 385 yards comes from a course adjustment made at the 1908 London Olympics so the race could start at Windsor Castle and finish in front of the royal viewing box.
How long does it take to run 26.2 miles?
This varies enormously by runner and pace — recreational finishers often take 4-6 hours, while elite marathoners finish in around 2 hours. If you’re planning your own training timeline, check out our guide on how long it takes to train for a marathon.
Related reading:
How to Train for Your First Marathon
How Long Does It Take to Train for a Marathon?
Marathon Training Plan for Beginners: The Complete Guide
What Is a Boston Qualifier Marathon? A Complete Guide to BQ Standards
Ready to run 26.2 miles through the heart of St. Petersburg? Learn more about the St. Pete Marathon course.