How many miles is a 50K?

A 50K is 31.07 miles, rounded to two decimal places from 50 km using the conversion factor above.

How many km is 50 miles?

50 miles is 80.47 km, rounded to two decimal places using the conversion factor above.

How many miles is a 100K?

A 100K is 62.14 miles, rounded to two decimal places from 100 km using the conversion factor above.

How long is a 100-mile race in km?

A 100-mile race is 160.93 km, rounded to two decimal places using the conversion factor above.

Is a 50K an ultramarathon?

Yes. A 50K is 50 km, which is longer than the marathon distance of 42.195 km, so it meets the definition of an ultramarathon.

Ultramarathon Distances: 50K, 50 Miles, 100K and 100 Miles

What counts as an ultra

Ultramarathon describes a distance beyond the marathon, rather than a single fixed race length. Both trail and road ultras fit that definition; the surface does not decide whether a race is an ultra.

The conversions below use 1 mile = 1.609344 km and are rounded to two decimal places. Divide kilometres by that factor to get miles; multiply miles by it to get kilometres. The marathon’s 26.2-mile figure above is the familiar rounded label.

50K: 31.07 miles

A 50K is 50 km, which converts to 31.07 miles. The K refers to kilometres, so a 50K and a 50-mile race are different distances.

Because 50 km is longer than the marathon’s 42.195 km, a 50K is an ultramarathon. When comparing listings, check whether the advertised distance is in kilometres or miles before choosing a race.

50 miles: 80.47 km

A 50-mile race converts to 80.47 km. Multiplying the distance in miles by the conversion factor gives the kilometre equivalent; this is not another name for a 50K.

If you use kilometres to plan your running, keep the converted distance alongside the original race label. That makes comparisons with kilometre-based events clearer.

100K: 62.14 miles

A 100K is 100 km, which converts to 62.14 miles. As with a 50K, the K means kilometres rather than miles.

For a reader used to miles, this conversion puts a 100K on the same scale as mile-based races. A 100K and a 100-mile race should remain separate options when comparing distances.

100 miles: 160.93 km

A 100-mile race converts to 160.93 km. The mile-based name is the starting input; the kilometre figure is its rounded equivalent.

Distance is a useful first filter for both road and trail ultras. Read the organiser’s course information before choosing an event: the conversion alone describes length, rather than the experience of a particular route.

Timed and backyard formats

In 24-hour and other timed races, the result is scored by distance covered in the allotted time. The time is fixed, while the distance depends on what the runner completes.

A backyard yard is 6.7056 km. This is a loop distance, rather than a fixed total race distance. When comparing backyard, timed and fixed-distance formats, distinguish the length of a loop from the distance recorded for the whole event.