How far is an ultramarathon?

An ultra starts beyond the marathon

An ultramarathon is a footrace longer than the standard marathon distance of 42.195 km, about 26.2 miles. It does not have one fixed length. A 50K and a 100-mile race both belong to ultrarunning, although the days they involve can be very different.

The definition explains the category; it does not tell you how hard an event will feel, what equipment it requires or whether it suits your current preparation. Read a race name as the beginning of the investigation. The route, time limits and support arrangements fill in the rest.

A 50K is a useful distance to recognise because it is a common step beyond the marathon and an IAU discipline in its own right. There is no requirement to keep moving through ever-longer distances. You can enjoy racing 50K without treating it as an entrance exam for 100 miles.

• World Athletics: what ultrarunning means
• International Association of Ultrarunners: disciplines

The common distances, side by side

K means kilometres. A race labelled “50 miles” is substantially longer than 50K, and 100K is substantially shorter than 100 miles. Check the units in the event details, especially when a race name uses only a number.

Equal distance does not mean equal demand

Imagine two advertised 50K races. One follows smooth riverside paths; the other includes steep climbing, rocky descents and navigation. The distance label is the same, but the skills, pace and preparation may differ considerably.

Look at total ascent and the elevation profile together. Total ascent adds up the climbing across the route. The profile shows where that climbing occurs, including whether a large climb waits near the finish. Also inspect the surface and the descent: downhill distance is not automatically fast or straightforward.

Write down the parts of the course you can practise and the parts that would be unfamiliar. This is more useful for choosing a first event than trying to turn every metre of climbing into a universal time penalty.

• Surface: road, smooth trail, mud, rocks, sand or a mixture.
• Ascent and descent: how much there is and where it falls in the route.
• Setting: exposure, altitude, darkness and possible conditions.
• Support: distance between checkpoints, route markings and access to supplies.

• Choose a first ultra that fits your circumstances

Use the distance to examine the timetable

A useful first calculation is the total time limit divided by distance. For a hypothetical 50 km race with a ten-hour cutoff, that gives 12 minutes per kilometre overall. Overall means everything: running, walking, refilling bottles and all other stops.

If you allow one hour for stops, nine hours remain for moving, which works out at 10 minutes 48 seconds per kilometre. Neither number is a recommendation or a prediction. They are a way to ask whether a particular timetable deserves closer investigation.

Check intermediate deadlines as well as the finish. The course may demand different speeds in different sections, so the overall average cannot tell you whether you will reach each checkpoint in time. Keep the exact start wave and the organiser’s definition of each cutoff with your notes.

• Build a checkpoint and stopping-time budget

Some events set the time instead of the distance

In a fixed-distance event, the distance is set and your finishing time is the result. In a timed event, the time period is set and your covered distance is the result. A 24-hour race, for example, does not promise that every entrant will cover the same number of kilometres.

Participation in a timed event does not automatically mean your own total exceeds the marathon distance. Check how the organiser counts laps or partial laps, and how results are recorded. The event format and your personal distance are different pieces of information.

Stage races divide a route into separate stages. A total of 250 km over several stages does not mean every stage is an ultramarathon, or that each stage has equal distance. Read the daily schedule alongside the overall total. A continuous race can also last several days, but the clock keeps running through rests.

• IAU: the 24-hour format
• Understand the different ultra race formats

Read the actual course distance

Treat “50K” or “100K” in a listing as something to confirm on the route page. Establish whether the organiser publishes an exact measured distance, an approximate trail distance or a category name. Check that the route file belongs to the edition and option you are considering.

If your watch later records a different total, keep that separate from the official result. Ask the organiser about an important discrepancy rather than assuming the watch figure proves the course was right or wrong. For planning, keep using the event’s current route and instructions.

A useful note contains five things: distance and units, ascent, format, finish limit and source date. With those on one line, you can compare options without repeatedly reopening tabs or accidentally mixing editions.

Choose the experience before the bigger number

Once the distances make sense, start with the kind of day you want and the preparation you can realistically do. A nearby supported 50K, a road ultra and a multiday event offer different experiences. The longest available distance does not have to be the most interesting one for you.

Make a shortlist of two or three events and compare their actual routes and arrangements. If a timed or multiday format appeals, our sister publication Multiday Running explores those subjects in more depth. Here, the first-ultra guide gives you a worksheet for making the initial choice.

• Build your first-ultra shortlist
• Explore timed and multiday running