THE Complete Guide to Ultramarathons

A beginner's guide to ultramarathons: distances, gear list, popular races, and tips.

August 03, 2021
If you purchase a product from one of our links below, we may earn a percentage from one of our affiliate partners. This does not impact how we review products. Read more about our review process and affiliate partners.

In this post, you will learn what ultramarathons are, what sets them apart from other types of races, and who should (and shouldn't) consider taking part in an ultra event.

You'll also find out how to prepare for your first race. We'll cover training, gear, and give you a break down of the 10 most popular ultras across the globe.

In fact, these are the strategies, tactics, and know-how that have helped me run 10 ultras (including the infamous Marathon des Sables) and set 3 fastest-known times to date.

Ready? Let's dive right in.

What is an Ultramarathon?

Essentially, an ultramarathon is anything longer than a marathon (ie. 26.2 miles).

However, there are typically four distances in the ultramarathon distance: 50km, 50 miles, 100km, and 100 miles.

Ultramarathon has risen in popularity through the exploits of legendary runners like Kilian Jornet, who not only has won most of the prestigious ultramarathons around the world, but also has set speed records for the ascents of Mont Blanc, Kilimanjaro, and Everest to name but a few.

Another notable name to set the ultrarunning world alight is UK-based Tom Evans who burst into the ultra scene at the Marathon des Sables (aka the toughest foot race on the planet) in 2017. He entered as a bet a year after taking up running and finished third.

Fun Ultramarathon Facts:

  • Ultramarathons have seen a 1676% increase in popularity in 23 years.
  • Only 0.03% of the US population having taken part in one. The US is, however, the biggest participant country when it comes to Ultramarathons around the world.‎
  • ‎In 2018, only 16% of those that took part in ultramarathons were women.
  • Both genders are equal when it comes to pace. The longer distance, the smaller the gap. And, over 195 miles, women are faster than men and you regularly see women winning races overall in ultra-distance races.
  • ‎The average pace of an ultra-runner is almost equal regardless of their age: 14:40 min/mile‎.
  • ‎The average age of ultra-marathoners in the USA is over 40.

Credit: Mannytheyellow (CC BY-SA 4.0)

Al Marmoom ultra departure lineStarting line of the Al Marmoom ultramarathon

Why Run an Ultra?

1. The Experience

Ultramarathons take place in some of the most beautiful parts of the world along trails you just wouldn’t see otherwise. Compared to marathons and shorter races, time is less relevant and the focus is more on the experience you have.

2. The Challenge

The first thing people ask when you do an ultra is not “how fast did you do it in?” but more likely “how did you do that?!” Running an ultra forces you to push both your physical and mental limits in ways no other sport does.  

3. The Food

There is a popular quote around ultramarathon running that it is an "all-you-can-eat buffet with a bit of running". That's because of the amazing aid stations set up at ultras serving burgers and fries instead of the gels and banana pieces that you would typically find at a road race aid station. Because you need so much fuel to keep going for hours on end, your stomach will usually rebel against gels after a while.

runner holding on a rope

James during the Marathon Des Sables ultra race

Are Ultra Marathons Bad for You?

With the slower pace and off-road terrain being kinder on the joints, ultrarunning typically is kinder to your body than any other sort of running.

Here are the three main reasons runners may be forced to quit a race before the finish line though:

1. Injuries

Musculoskeletal injuries are of course common among ultrarunners, resulting from the huge mileage you put through your legs and the difficult terrain you might face.

60% of ultrarunners stated that they have picked up some sort of injury in the last 12 months. These are typically short-term injuries caused by tripping on terrain while out on the trails or through overtraining.

The most common ones are shin splints, runners knee, and ankle pain.

2. Dehydration

During races, the most common problem that causes a runner to have to pull out is dehydration. In a recent 161km race, the top ten finishers had lost more than 2% of their body weight by 90km from dehydration.

While drinking water may be considered enough, it is crucial to avoid dehydration to also consume sodium to ensure that the water is actually absorbed into the body.

Diarrhea and vomiting can also be triggered by dehydration and cause long-term health issues if not taken care of quickly.

3. Gastrointestinal Issues

Gastrointestinal issues are also a huge cause of runners failing to reach the finish line. Runner’s Trots, to call it by its British term, is caused by the churning of miles of running twinned with the varying diet you might be having during the race. That's why, below, we encourage runners to try out the food they might eat during the race long before race day.

Jacob Resor (CC BY 2.0)

barkley ultramarathon in TennesseeThe Barkley ultramarathon in Tennessee

How to Prepare For a 100-Mile Ultramarathon?

"I like to be outside and just be in the mountains – that's the best training for me. And what I do least – in fact, not at all unless I’m injured – is gym or indoor training."

- Kilian Jornet

First, complete a standard 26-mile marathon. This will ensure you're in good shape before you attempt an ultra. Here's a sample 4-month training plan if you're just getting started.

Now that you can run a marathon, Increase the mileage by no more than 10% a week to ensure that you don’t overtrain and that the experience remains rewarding and enjoyable. Continue until you reach the desired mile goal, then taper down as you get closer to race day to avoid injuries and maximize your readiness.

The slow build-up to an ultramarathon is key to avoid any injuries through overtraining. With that said, you would be looking for a training plan of:

  • 6 months if you have been training for a marathon
  • 12 months if you are starting from scratch

Here is a rough timeline of what your milestones might look like, leading up to the race: 

Time Mileage Goal
Months 1 to 4 26 miles
Month 5 32 miles
Month 6 38 miles
Month 7 56 miles
Month 8 75 miles
Month 9 91 miles
Month 10 - Race 100 miles

Note: It is highly unlikely that you will run all of an ultramarathon, so train accordingly. While training for an ultramarathon, I will do about 30% of my miles at a walking pace if not more. 

marathon runners running long distanceRun a marathon several months before attempting an ultra.

Let's get into the weeds of the actual training. 

The two key things to introduce into your training in going from a half marathon or marathon to an ultramarathon is strength training and time on feet.

  • Strength training is a an asset for most runners. But when you are spending hours and hours on your feet, it isn’t just important but necessary. Strengthen your legs and core.
  • Time on your feet is simply that, regardless of pace or distance just getting hours of experience on your feet plays dividends come race day.

A typical week of ultramarathon training will include running, cross-training and rest.

Monday Tuesday Wednesday Thursday Friday Saturday Sunday

Timed run

Timed Run
Mile Run*

Timed Run (easy)

*: increase in 5% to 10% increments each week.

grand to grand marathon 2012

Ultramarathon Gear List

This is very subjective compared to marathons or shorter distances as the demands vary hugely race to race, from mountain races to deserts multi-day races.

But below is what I would use for a typical ultramarathon. Note I've come up with this gear list after hundreds of miles of trial and error.

👟 Shoes

Trail runners are the way to go. Depending on the terrain of your race, you might want to choose something with more or less grip. But comfort is key for anything over marathon distance. 

Here are some popular models amongst ultra runners. My personal favorites are the Inov-8 Trailfly for their cushioning and long life span.

  • Inov-8 Trailfly Ultra 300 G
  • Brooks Cascadia
  • Mizuno Daechi
  • Nike Wildhorse

🧦 Socks

Always have a spare pair in your race pack to avoid blistering or as a treat for those river crossings or wet days. Injinis (toe socks) are a great option as they offer extra protection against blister, and comfort.

🩳 Shorts

While you might pack waterproof trousers for ultramarathons, you will wear shorts while you're running. Lycra or lightweight and loose depending on the weather and you feel comfortable in. Watch out for chafing, which can be prevented by applying chamois cream around your thighs.

ultra runner carrying two water bottles

🎽 Top

Similar to shorts, it is very much a personal preference. I will wear a lightweight technical top for breathability but will have a long sleeve extra layer in my race pack. As far as fabric goes, nylon and polyester are the most popular choices. Both are comfortable and breathable. No cotton whatsoever.

🎒 Race Pack

Depending on the distance of your race and how dispersed the aid stations are along the way, the size of your pack will vary greatly. You'll find race packs as small as 1.5 L and as large 25+ L (used for longer races). Choose the rest of your gear first, then look for a pack where it'll fit. Again, check the race's official website for specific recommendations.

Your pack will typically contain your race-day nutrition, water, a first aid kit, and any spare items you want to bring along (eg. socks). Runners usually use collapsible water pouches that can be folded when not in use.

🏃‍♂️ Poles

Using trekking poles makes a runner 30% more efficient over the distance of an ultra and helps avoid fatigue and injuries caused by over-stressing the legs.

Recommended: Leki Micro Pro.

runner on a desert

Credit: James

Top Ten Ultramarathons

Race Location Month Distance
Comrades South Africa June 56 miles
UTMB France August 106 miles
Western States 100 USA June 100 miles
Badwater 135 USA July 135 miles
Barkley Marathon USA March/April 100 miles
Marathon des Sables Morocco April 155 miles
Dragon's Back Race UK September 224 miles
Grand to Grand USA September 140 miles
6633 Arctic Ultra Canada February 380 miles
Everest Trail Race Nepal November 19 miles
comrades ultramarathon race map


  • Location: South Africa
  • Date: June
  • Distance: 56 miles
  • Avg. Attendance: 27,500
  • Elevation gain: 6,600 ft

With over 27,500 runners and started all the way back in 1921, Comrades holds the title of oldest and largest ultramarathon on the planet. The 90km legendary ultra has a strict cut-off of 12 hours as you run from Durban to Pietermaritzburg (or Pietermaritzburg to Durban, depending on the year).

Visit Comrades’ official site to register for their next event.

UTMB ultramarathon race map


  • Location: France
  • Date: August
  • Distance: 106 miles
  • Avg. Attendance: 2,300
  • Elevation gain: 32,800 ft

Arguably the pinnacle of mountain running the Ultra-Trail du Mont Blanc is a Mecca for the elites of running. Following the route of the Tour du Mont Blanc UTMB takes you through France, Italy, and Switzerland as you run its epic 171km and with over 10,000 metres of elevation gain, it is not for the faint of heart with only about 60% finishing the race.

Visit UTMB’s official site to register for their next event.

Western States ultramarathon race map

Western States 100

  • Location: USA
  • Date: June
  • Distance: 100 miles
  • Avg. Attendance: 400
  • Elevation gain: 18,000 ft

The world’s oldest 100-mile trail race, Western States 100 is considered the world’s toughest single stage foot race. A race that started life off as a 100-mile horse race, until someone turned up without a horse and ran anyway is now the top ultramarathon in the world (although a few of these in the top ten would argue otherwise!).

Running through the Sierra Nevada Mountains in California, Western States sees the best of the ultrarunning world compete with the record currently standing at 14 hours and 9 minutes by American; Jim Walmsley.

Visit Western States 100’s official site to register for their next event.

Badwater ultramarathon race map

Badwater 135

  • Location: USA
  • Date: July
  • Distance: 135 miles
  • Avg. Attendance: 90
  • Elevation gain: 13,000 ft

A 135-mile foot race is enough to put most runners off but with this race taking place in Death Valley in the Nevada Desert the distance isn’t the thing that usually stops runners from finishing but the extreme heat. With temperatures reaching 130F (54C), runners go to extreme lengths to avoid the heat getting the better of them, like wearing ice packs at every possible crew spot and other cooling strategies and working out which shoes won’t melt on the tarmac.

Visit Badwater 135’s official site to register for their next event.

Barkley ultramarathon race map

Barkley Marathon

  • Location: USA
  • Date: March/April
  • Distance: 20 miles (five loops)
  • Avg. Attendance: 15
  • Elevation gain: 60,000 ft

This legendary race has been the subject of a Netflix documentary due to its abnormal rules and eccentric organizer. Barkley Marathon takes place in Tennessee every year with runners having to apply secretly and the entry fee is $1.60 and whatever the race founder Lazarus Lake needs that year (one year it was T-shirt’s). He will pick the 40 runners with one given bib number one chosen as the human sacrifice, the runner least likely to finish.

There have been only a handful of finishers of the five loops of the 20-mile course due to the huge elevation gain (60,000 feet) and the terrain being brutal and the weather usually too.

Visit Barkley Marathon’s official site to register for their next event.

Marathon des Sables ultramarathon race map

Marathon des Sables

  • Location: Morocco
  • Date: April
  • Distance: 155 miles
  • Avg. Attendance: 1,200 
  • Elevation gain: 8,200 ft

A race I took on in 2018, known as the toughest foot race on the planet, the Marathon des Sables takes place in the inhospitable Sahara Desert. You carry all your kit and food for the week with you as you battle the sand and blistering desert heat for 250km over six days. Sleeping in traditional Berber tents under the incredible star-filled sky is an experience that should be on everyone’s bucket list.

Visit Marathon des Sables’ official site to register for their next event.

Dragon's Back ultramarathon race map

Dragon’s Back Race

  • Location: UK
  • Date: September
  • Distance: 224 miles
  • Avg. Attendance: N/K
  • Elevation gain: 57,000 ft

From Conwy Castle in the North to Cardiff Castle in the South, a legendary multi-stage, ultra running journey down the spine of Wales. The 360km race has over 57,000 feet of elevation gain (twice the height of Everest) and with it all self-navigated and self-sufficient it is not for the faint of heart and unsurprisingly the race has been the subject of many documentaries charting runners across the stunning mountainous landscape. It is a race I took in 2022.

Visit Dragon's Back Race’s official site to register for their next event.

Grand to Grand ultramarathon race map

Grand to Grand

  • Location: USA
  • Date: September
  • Distance: 140 miles
  • Avg. Attendance: N/K
  • Elevation gain: 8,700 ft

This multi-day race takes you from the rim of the Grand Canyon to the top of Grand Staircase in one of the remotest parts of America. While the distance per day (averaging 20 miles a day for seven days) isn’t as arduous as those listed above the heat of the Utah and Arizona desert is not to be taken lightly.

Visit Grand to Grand’s official site to register for their next event.

Arctic ultramarathon race map

6633 Arctic Ultra

  • Location: Canada
  • Date: February
  • Distance: 380 miles
  • Avg. Attendance: 30
  • Elevation gain: 2,300 ft

While most of these races tackle the heat of the desert, 6633 is the other extreme. This non-stop self-sufficient foot race in the Yukon is either 120 or 380 miles with both crossings into the Article Circle. Not only do you have to battle winds of up to 120km/h and temperatures as low as -40C you also have to carry all you need for the race (food and gear) in a sled with only two bag drops for the 380 miles distance.

Visit 6633 Arctic Ultra’s official site to register for their next event.

Everest Trail ultramarathon race map

Everest Trail Race

  • Location: Nepal
  • Date: November
  • Distance: 19 miles
  • Avg. Attendance: 50
  • Elevation gain: 1,300 ft

Walking at altitude can be extremely difficult let alone running 170km over six days. So while the longest day of this multistage race may only be 31km this race is considered one of the toughest physical challenges out there. But while it might be incredibly arduous just breathing at 4,100m above sea level having the highest mountain in the world looming over you and following in the footsteps of Sir Edmund Hilary and Sherpa Tenzing promises to make the suffering worth it.

Visit Everest Trail Race’s official site to register for their next event.

Thru-Hiking VS Ultra-Running

Compared to the Appalachian Trail, a 100 miler is like an anaerobic exercise. It’s like a sprint. You do hurt really badly in an ultra. On the trail, you hurt, too, but it’s a longer, duller pain. If you try to hurt the same way you do in a 100-mile race, you’re going to burn out.

- Jennipher Pharr Davis

On the face of it, there is very little difference between ultramarathon-running and thru-hiking.

Both sports work out the same muscles, are fueled with similar food, share the same trails, and burn a similar amount of calories. Some would argue that thru-hiking is the purist version of ultra-running.

However, there are a two primary differences to observe.

  1. Pace: Ultramarathons do consist of some hiking but are primarily running events. So some running is expected. Also, distance for a thru-hiker is fluid with hikes tending to span across many days with flexible finish lines each day. Ultramarathons, however, have pre-set up campsites and aid stations and the distances is set and agreed upon. While they may share the same trails, ultra-running is an organized event whereas thru-hikers will go when, where, and however long they please.

  2. Gear: Thru-hikers tend to choose walking boots and thicker more comfortable clothing, ultrarunners pick trail running shoes and their kit is lightweight, aiming to save every little gram in search of faster times.

The gap between the two activities is narrowing however, with the rise in popularity of FKTs (Fastest Known Times). These are speed records set on long-distance trails such as the PCT or Appalachian Trail. Jennifer Pharr Davis and Scott Jurek are two FKT record-setters well-known  in both the ultra and thru-hiking communities.

The current FKT for the Appalachian trail stands at 41 days and 7 hours for the 2,189-mile trail and the PCT’s record is 52 days and 7 hours for the 2,592 miles, both of which are currently held by Belgian dentist: Karen Sabbe.

runner with trekking poles

Credit: mako10


Longest ultra in the world?

The longest ultramarathon in the world spans 3,100 miles. Known as the Self-Transcendence, it takes place over several weeks in Queens, New York, and is a 0.5-mile loop of one city block. Finishers take home a t-shirt, a DVD and a simple small trophy.

This race is the extreme end but it highlights the no-frills approach that ultramarathons encapsulate.

James Dunn photo

About James Dunn

By James Dunn: James is a UK-based ultrarunner, blogger and coffee addict. You can follow his journey to run every trail and promote the mental health benefits of the great outdoors along the way on his instagram at @morningcoffeerun or on his blog.

About Greenbelly

After thru-hiking the Appalachian Trail, Chris Cage created Greenbelly to provide fast, filling and balanced meals to backpackers. Chris also wrote How to Hike the Appalachian Trail.

Stoveless Backpacking Meals
  • 650-Calorie Fuel
  • No Cooking
  • No Cleaning