A half marathon is defined as exactly half the distance of a full marathon (42.195 km). In official measurement it covers 21.0975 km, which when converted to imperial units equals 13.1094 miles. In practice, most events round this to 13.1 miles (21.1 km) for simplicity and marketing.
Official Distance
- Kilometers: The standardized distance is 21.0975 km, exactly half of the marathon’s 42.195 km course.
- Miles: Converting 21.0975 km yields 13.1094 miles, though this is almost universally rounded to 13.1 miles
Rounding Conventions
- 13.1 miles: Most race organizers and training guides refer to the half marathon as a 13.1-mile event, simplifying both timing chips and promotional materials.
- 21.1 km: Similarly, metric-focused events often label the distance as 21.1 km, rounding to the nearest tenth of a kilometer.
Whether you see it listed as 13.1 miles or 21.1 km, both represent the same officially measured distance of 21.0975 km (≈ 13.1094 miles) for a half marathon.
Ironman and Half Ironman Distances Table
| Event | Distance (km) | Distance (mi) |
|---|---|---|
| Marathon | 42.195 | 26.2188 |
| Half Marathon | 21.0975 | 13.1094 |
| 10 K | 10 | 6.2137 |
| 5 K | 5 | 3.1069 |
How Many Miles is A Marathon?
A standard marathon distance is 42.195 km, which converts to 26 miles 385 yards, or approximately 26.2188 miles (commonly rounded to 26.2 miles)
Official Distance
- Metric: The International Association of Athletics Federations (now World Athletics) fixed the marathon at 42.195 km in May 1921.
- Imperial: That metric distance equals 26 miles 385 yards, which is 26.2188 miles when expressed purely in miles.
Common Rounding
- 26.2 miles: In most race literature, the distance is rounded to 26.2 miles for simplicity.
- 42.2 km: Likewise, metric signage often shows 42.2 km, reflecting a one-decimal rounding of the exact 42.195 km length.
Historical Note
The unusual extra 385 yards dates back to the 1908 London Olympics, when the course was set from Windsor Castle to the Olympic Stadium’s Royal Box—later standardized by World Athletics in 1921.
