How to Choose Your First (or Next) Ultramarathon Distance

So you’re thinking about running an ultramarathon—amazing.

Maybe you’ve run a half marathon or marathon and you’re curious about going beyond 26.2. Maybe you just want an adventure. Or maybe you want to see what you’re actually capable of when you push past the familiar.

But here’s the big question: Which ultra distance should you choose?

There are several common race distances in the trail and ultra world—50K, 50 miles, 100K, and 100 miles—and each has a completely different vibe. Here’s how I break them down, based on racing them, coaching runners, and witnessing finish-line stories.

🏁 50K (31 miles) ~The approachable ultra

If you can hike for ~10 hours, you can finish a 50K.Seriously.

People overcomplicate it, but a 50K is really just a marathon with a snack break…on dirt. Of course most marathons do not have much for elevation gain so your training needs to include trails with similar elevation change per mile (Total elevation gain + total elevation loss / miles= elevation change per mile) and the knowledge that if you run a marathon on flat ground in 5 hours, you're going to be out there much longer.

Nutrition matters, but it doesn’t need to be a science project. Eat something every hour, drink fluids, keep moving forward.

Why I love the 50K:

• Once you've done a couple, you can push your effort!

• It’s a perfect “stepping stone” race if you’re working toward a bigger event.

• You can use it as a long training run before a 50-mile or 100K race.

• It can be a dress rehearsal—or it can be your main event.

• the average cut off time for a 50K race is 6-10 hours

If you’re curious about ultras but not ready to commit your entire life to training, a 50K is a fantastic entry point.

💪 50 Miles ~ Where you start to feel like a real ultrarunner

The vibe shifts at this distance.

You’re running an ultra—this isn't "just a long run."

Nutrition becomes more important. You’ll need to plan your fueling and hydration more intentionally, but one misstep likely won’t ruin your entire day.

The training commitment increases—noticeably.

What to expect:

• Your weekly mileage will need to climb.

• You’ll be moving for many hours.

• You’ll still probably finish before sunrise the next day… which is a win.

• the average cut off times for a 50 miler is 12-14 hours

  
  

You don’t necessarily need a huge crew or pacers. A 50 miler can still be done in a fairly self-supported way, which makes it ideal if you’re not interested in assembling a small race-day army.

🌙 100K (62 miles)~My personal favorite distance

The 100K is the magic middle ground—longer than 50 miles, but without the total life disruption of a 100 miler. Though, to be fair most people will feel training for any distance is a bit of a life disruption. The truly committed runners do it for the disruption though.

The 100K sits perfectly between “This is insane” and “This is actually doable.”

Here’s what usually happens in a 100K:

• You’ll finish in the dark.

• You’ll likely sleep in your own bed that night/early morning.

• Nutrition matters. A lot.

• A crew and pacer is really helpful, but not essential.

• the average cut off time for a 100k is 14-20 hours

  
  

A 100K feels like a full-on adventure while still preserving your weekend and your sanity. You get pushed to the edge, but not over it.

🔥 100 Miles~The distance that changes you

Training for a 100 miler is not a hobby. It becomes part of your life.

You will run in the dark.

You will train exhausted.

You will question why you signed up.

And then race day arrives and you remember: You signed up because you wanted to see what you’re capable of.

At this distance:

• Nutrition matters 100%—your stomach can make or break your race.

• A crew and pacers can change everything—mentally and logistically.

• You need support from your family—not necessarily on the course, but in life. Training takes time.

• Depending on the race, the average cut-off time is 24-36 hours (but some races, like UTMB have cut-offs as long as 46.5 hours)

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When you cross a 100-mile finish line, you don’t just get a belt buckle—you walk away a different person.

✨ So… Which One Should You Choose?

• Want to try an ultra? → Run a 50K

• Want a big challenge without losing sleep? → Run 50 miles

• Want the “ultra experience” without committing to a full 100? → 100K

• Want to transform your life? → 100 miles

  
  

Whichever distance you choose, you’ll come out stronger.

If you’re unsure where to start, or you want help building a training plan that fits your real life (job, family, time constraints), I’d love to chat.

💬 Drop a comment or send me a message—I love talking about this stuff.