By Lauren HollandUpdated November 2026
The first marathon, as legend has it, was roughly 40 kilometers, or about 25 miles, from the plain of Marathon to Athens. That legend is the basis for the modern race, but the distance you run today, 26.2 miles, was not fixed until 1921. This guide explains where the original distance came from, how it changed over time, and how to convert the numbers so you can picture the race.
What the Original Race Distance Was
The story most often told comes from the Greek writer Plutarch, who wrote centuries after the event. According to that account, a messenger ran from the battlefield at Marathon to Athens to announce the Greek victory over the Persians in 490 BC. Most historians treat the run itself as a later embellishment, but the route is real: the distance between Marathon and Athens is commonly given as roughly 40 kilometers (about 25 miles) by road.
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No ancient source records an exact mileage, so the 40 km figure is an estimate based on the geography. Keep that in mind when you compare it with the modern standard.
How the Distance Changed Over Time
The modern marathon was introduced at the 1896 Athens Olympics, and early races used a range of distances. The 1908 London Games are the key turning point. The course was set to run from Windsor Castle to the royal box at the stadium, and the distance came out to 26 miles 385 yards. The International Association of Athletics Federations later standardized that figure, and in 1921 the official distance was set at 42.195 km, which is 26.2 miles.
A quick comparison helps:
| Measure | Approximate distance |
|---|---|
| Legendary route, Marathon to Athens | 40 km (about 25 miles) |
| 1908 London course | 42.195 km (26 miles 385 yards) |
| Official standard since 1921 | 42.195 km (26.2 miles) |
How to Picture the Distance Today
If you are planning your own training around the first marathon distance, break the 26.2 miles into pieces you can manage. Most beginners find it useful to:
- Convert the distance to your local unit. 26.2 miles equals 42.195 km, and a common training block is a long run of 18 to 20 miles.
- Map a route with accurate measurement. Use a GPS watch or a calibrated course map rather than estimating by eye.
- Plan your long runs by time as well as distance. Many coaches prescribe 2 to 3.5 hours for the longest run, which varies with pace.
- Check your course split markers before race day so you know where each mile falls.
For a structured approach to the weeks leading up to race day, see How Long to Train for First Marathon: A 16–20 Week Beginner Guide, which shows how the long-run progression builds toward the full distance.
Why the Distance Matters for Your Training
Knowing the history explains why the distance feels arbitrary, but it does not change the physical demand. You will cover 26.2 miles on race day regardless of whether the original route was 25 miles or 26. Your training should prepare you for that exact figure. For background on the ancient race itself, When Was the First Marathon? The 490 BC Story and Key Dates covers the timeline in more detail, and How Fast Was the First Marathon? The 490 BC Story and Modern Times compares the historical and modern race experience.
Common Mistakes When Reading the Distance
- Treating the 40 km legend as the official length. The official length is 42.195 km.
- Mixing miles and kilometers when comparing race results or course maps.
- Assuming all early marathons were the same length. Distances varied before 1921.
- Trusting a course that is not measured. Verify it with a certified or GPS-measured route.
FAQ
Was the first marathon exactly 26.2 miles?
No. The 490 BC race is traditionally described as about 40 km (roughly 25 miles). The 26.2-mile distance was standardized after the 1908 London Olympics and made official in 1921.
Why is the marathon 26.2 miles?
The distance comes from the 1908 London Olympic course, which measured 26 miles 385 yards. The International Association of Athletics Federations later adopted that figure as the standard.
Do I need to know the history to run a marathon?
No, but knowing the distance and its origin can help you plan a realistic training schedule. Focus on preparing for the exact 26.2 miles you will race.
Conclusion
The first marathon was likely about 40 km, but the race you will run is 42.195 km, or 26.2 miles, fixed in 1921. Plan your training and course around that exact number. Confirm your route measurements before race day so you can pace with confidence.
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About Lauren Holland
Lauren Holland is part of our editorial team and reviews and edits our marathon & half-marathon guides, checking product details against manufacturer specifications and owner feedback.
