If you keep reading about them, you already want to. Most ultras let you walk, most are on trail, and the people at the back are the ones out there the longest. Pick a race with a time limit you can see yourself inside.
That is the whole answer. The rest of this post is the part that makes it believable, because you have probably had the question for a while and told nobody.
An ultramarathon is any race longer than a marathon. The shortest common one is the 50K, about 31 miles. Past that you get 50 miles, 100K, 100 miles and longer. They are a different sport from road racing, and that difference is what lets a lot of people in.
Can I run an ultramarathon?¶
Probably yes, and "run" is doing less work in that sentence than you think.
Ultras are moved along by walking. Steep climbs get hiked, and people at every position do it. Aid stations are places to sit and eat, and nobody is judging how long you stay. The pace is slow enough that you can hold a conversation for hours, which is why the back of the field is such a good place to be.
What decides whether you finish is mostly time on your feet. Can you keep moving, with food and water going in, for the hours the race gives you? That is a trainable thing, and it responds to months of showing up, not to a fast 5K.
Two things I cannot answer for you. One is whether your body has a medical reason to be careful. If you have a heart condition, a recent injury, or anything else a doctor has told you to watch, talk to your doctor or a sports medicine physician before you sign up. The other is whether you want it. Only you know that one, and the fact that you are reading this is a decent sign.
Am I ready for an ultra if I have only run a half marathon?¶
You are closer than you think, and you have more time than you think.
A half marathon tells you that your body handles a couple of hours of running. A first 50K asks for something longer, but you do not have to get there this month. You pick a race far enough out, usually several months, and build toward it. Your long run gets longer, some of it becomes walking on purpose, and you practice eating while moving. That last one trips up people with plenty of fitness.
If you have never run a marathon, you can skip that step. Plenty of people go from a half marathon straight to a trail 50K, and plenty go from a few years of casual running. If you are coming back after time away, the same applies. The race does not ask what you did last year.
Here is what building toward it looks like in practice. One run a week gets longer than the others. On that run you walk the hills from the first week, so that walking is a skill you own and not a defeat you meet at mile twenty. You carry what you will eat in the race and eat it, so your stomach has met it before. Some weeks you run on trail, because ankles and hips need to get used to uneven ground. None of that needs speed. It needs hours, and hours are something anyone can collect.
The first 50K training guide lays out a 12-week build if you want to see what the work looks like on paper. Look at it before you decide anything. A plan you can read is less frightening than one you are imagining.
What if I am too slow for an ultra?¶
This is the worry that keeps the most people from signing up, so here is how it works.
Every race with a finish line has a time limit, and the limit is the only pace that matters. The runners at the back are not being tolerated. They are out there the longest, and they see the most of the course.
So do not ask "am I fast enough." Ask "can I stay inside this particular race's limit." Those are different questions, and the second has an answer you can look up. Every race publishes its own cutoffs, and they differ from race to race. You are choosing which one to enter.
Here is a plain way to test it. Take a race's time limit and divide it by the distance. That gives you the slowest average pace the race will accept, including every minute you spend at an aid station and every hill you hike. Now think about a long, easy day on your own legs, with walking in it. If the race's number is slower than that day, the race has room for you. If it is not, look at the next race. There are a lot of them.
That is the work. You are not training to be quicker. You are choosing a race where the clock suits the runner you are now.
What distance should my first ultra be?¶
The 50K is the usual first one, and it is a good one. It is long enough to be a real ultra, and short enough to build toward in a few months. If that sounds like what you want, take it.
Other starts are fine too. Some people go straight to 50 miles because they like the idea of a longer day. Some run a 100 as a first ultra, with a pacer and a plan, and finish. The distance matters less than what is around it:
- The time limit. Can you see yourself inside it with room to spare?
- The terrain. A trail race that suits where you already run will feel easier than one that does not.
- The date. Enough months out to build without cramming.
What it feels like out there¶
I will tell you one thing I know.
At mile sixty, in the dark, I wanted to be done. A stranger handed me broth, walked the next climb with me, and talked about nothing until I could run again. I never got their name. I still think about them on every hard climb.
Months later, on a training run, I fell in beside a runner who was hurting and matched their pace without thinking about it.
That is what you are signing up for, past the distance. The course is hard and the night is long. The people are what get you through it, and then you become one of them.
How to pick a first race¶
Start with the time limit and work backward. Open the race catalog. It lists each race's cutoffs, crew access, drop bags and where your people can park, and none of it needs an account. Find a few races in the next six to twelve months that sit near where you run. Read each one's time limit and ask the question from earlier: can I see myself inside this?
Then pick one and put the date in your calendar. The runner who has read about these races for a year and told nobody usually needs one thing, which is a date. The rest gets built around it.
If you want to know who built this and why, there is a page for that: About NavRun.
You already wanted to. Pick the race. navrun.app/ultras