This ultramarathon guide covers distances, training, nutrition, gear, and how to get started — everything you need before committing to a race. An ultramarathon is any race longer than a standard marathon: longer than 26.2 miles, or 42.195 kilometers. Beyond that, there is no fixed distance. The word covers an enormous range — a 50-kilometer trail race you might finish in under five hours, a flat 50-mile desert race, a mountain 100k with 6,000 meters of climbing, and a 100-mile course that keeps most runners moving for more than 24 hours. They are all ultramarathons.
If you are already decided on a distance, jump straight to the training guide for that distance in the section below. If you are still figuring out where to start, this guide covers the full picture: distances, how ultras differ from road marathons, training, nutrition, gear, and how to pick your first race.
Ultramarathon Distances: How Long Is an Ultra Marathon?
The official definition from World Athletics is simple: an ultramarathon is any footrace longer than 42.195 kilometers. Beyond that, there is no single standard distance. Ultramarathons are defined by the course, not by a fixed length.
The most common ultramarathon distances are:
Distance | Kilometers | Miles | Typical Finish Time | Who It’s For |
|---|---|---|---|---|
50k | 50 km | 31 miles | 5–8 hours | First ultra, strong marathon runners |
50-mile | 80 km | 50 miles | 9–14 hours | Experienced ultra runners |
100k | 100 km | 62 miles | 12–20 hours | Intermediate to advanced |
100-mile | 161 km | 100 miles | 22–36 hours | Advanced ultra runners |
Fixed-distance races — 50k, 100k, 100 miles — are the most common format. Time-based ultras, where you run as far as possible in a set window, are a growing alternative. Backyard ultras, where runners complete loops until only one person is left standing, are the most popular format in this category.
Most ultra runners begin at the 50k. It is long enough to require genuine ultra preparation but short enough that the training and race are manageable alongside work and normal life. The 50-mile is often the next step. Some runners go directly from 50k to 100k depending on goals and race availability.
How Is an Ultramarathon Different from a Marathon?
Running a marathon does not fully prepare you for an ultra. The differences go beyond distance.
Terrain. Most ultramarathons are on trails, not roads. That means hills, technical footing, loose rock, mud, roots, and constant small adjustments that make trail running more demanding per kilometer than road running.
Elevation. Trail ultras often involve thousands of meters of climbing and descent. A 50k with 2,500 meters of gain is a fundamentally different race from a flat 50k. Many ultra training plans are structured around vertical gain, not just kilometers or miles.
Pace. Ultra running pace changes constantly with terrain. You will run fast sections, walk steep climbs, and shuffle technical descents. Effort-based training using RPE — Rate of Perceived Exertion — is more useful than fixed paces.
Time on feet. Even a short ultra like a 50k can keep you moving for five to eight hours. Fueling, hydration, gear management, and mental endurance across that time are their own training categories.
Fueling. At marathon distances, gels and water can get you through. At ultra distances, your body needs real calories — solid food, not just quick-digesting gels — and you need to practice eating while moving.
Self-reliance. Ultras often require mandatory gear, navigation between aid stations, and real-time decisions about blisters, cramping, and fatigue. These are skills you develop in training, not on race day.
Who Runs Ultramarathons?
Ultra running has grown significantly over the past decade. It is not a sport for a narrow elite. Most race fields are mixed, with finishers ranging from competitive athletes to people running their first event in their 50s. The sport does not select for body type, speed, or prior race resume. It selects for patience, consistency, and willingness to spend a lot of time on your feet.
A typical ultra field includes runners who finished their first marathon the year before, runners who have been trail running for decades, and everyone in between. What most ultra finishers share is not pace — it is the discipline to train consistently and the mental composure to manage difficulty across many hours.
You do not need to be fast to run an ultra. You need to be prepared.
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How to Get Started in Ultra Running
The path into ultra running is more accessible than most people expect. You do not need a specific race resume, a target finish time at a shorter distance, or years of trail experience. You need a reasonable aerobic base, a willingness to spend time on trails, and a training plan that builds toward your specific distance.
A practical starting point:
You can run comfortably for 90 minutes at an easy effort without feeling wrecked afterward.
You have several months of consistent running behind you.
You have some experience on uneven terrain — it does not need to be technical, but flat pavement alone is not enough.
If you check those boxes, you are ready to pick a distance and start building.
Choose Your First Ultra Distance
The right first distance depends on your current fitness, available training time, race calendar, and how long you want to be on your feet come race day.
Trail Marathon — The Road-to-Trail Step
If you are moving from road running to trails and want a demanding goal race that is not yet a full ultra, a trail marathon is an excellent entry point. Trail marathons are not easier than road marathons — terrain and elevation make them harder per kilometer — but the training block is focused and the distance is achievable for runners with a solid road base.
Read the complete trail marathon training guide →
50k — Your First Ultra
The 50k is the most common first ultra distance for good reason. It is long enough to require specific ultra preparation but short enough that the training fits into most schedules. Most runners who finish a 50k describe the race as more manageable than expected when they had prepared correctly. If you want to call yourself an ultramarathon runner, the 50k is where most people start.
Read the complete 50k training guide →
100k — Intermediate Ultra
The 100k is a meaningful step up from the 50k. It requires more training volume, more experience managing fatigue across many hours, and a different approach to pacing, fueling, and mid-race problem solving. Most runners who target a 100k have at least one 50k or 50-mile behind them — though exceptions exist for runners with a strong fitness background and smart preparation.
Read the complete 100k training guide →
100-Mile — The Classic Ultra Distance
The 100-mile is the race that defines ultra running for many people. It requires serious training volume, experience at shorter distances, night running, and the ability to manage a race that will last at least 22 hours for most finishers. It is not a beginner event, but it is achievable for runners who have built systematically toward it.
How to Train for an Ultramarathon
Ultra training is built on three foundations: time on feet, elevation, and consistency. You are not optimizing for speed. You are building the aerobic base, muscular durability, and mental resilience to keep moving for hours under load.
Train by Time, Not Miles
In road running, weekly mileage is the standard training metric. In ultra running, weekly hours are more useful. A three-hour trail run over hills might cover far fewer kilometers than a three-hour road run, but it creates a larger muscular and aerobic training load. Building toward six to ten hours of running per week — depending on your target distance and phase of training — tells you more than any mileage number.
Make Elevation a Training Priority
Most trail ultras involve significant climbing and descent. Climbing builds aerobic capacity and specific leg strength. Descending builds the eccentric quad durability you need to keep moving in the final stages of a race. If your home terrain is flat, hill training is a specific skill to develop deliberately — not something to improvise during race week.
Read the complete guide: How to train for hills when you don’t have access to mountains →
Build Long Runs Progressively
The long run is the backbone of ultra training. It should build week by week through your plan and include sections run at race effort — not just easy shuffling. Practice your fueling, hydration, and gear on long runs. These are race-day skills, not just fitness activities.
Back-to-back long runs on consecutive days are a useful ultra-specific tool. Running a moderate effort on tired legs teaches your body to keep moving when freshness is gone — which is exactly what happens in the later stages of a 100k or 100-mile.
Add Targeted Strength Work
Trail running demands more from your hips, ankles, and lateral stabilizers than road running does. Single-leg exercises, hip stability work, and calf strength all reduce injury risk and improve efficiency on technical terrain. One or two short strength sessions per week is enough for most runners during a build.
Train Specifically for Your Distance
Each ultra distance has its own demands. A 50k training block looks different from a 100-mile block in volume, structure, and key sessions. Start with the distance-specific guide that matches your goal race — each one covers the full training structure for that distance.
Ultramarathon Nutrition: How to Fuel for Hours
Nutrition is one of the most undertrained and most important aspects of ultra running. Getting it right separates a strong finish from a mid-race collapse. Getting it wrong is the most common reason experienced runners DNF.
Calorie Targets
A practical starting range for most ultra runners is 200 to 300 calories per hour. That range is a guideline, not a formula. Your actual needs depend on body size, pace, heat, and how well your gut handles food while moving. At lower intensities in longer races, some runners can absorb more. In shorter, faster races, some manage well at the lower end.
The error most first-time ultra runners make is not eating enough early in the race when they feel fine — then paying for it in the final third when calorie deficit has accumulated.
Carbohydrates Are the Primary Fuel
Your body runs on carbohydrates at running intensities. Gels, chews, sports drink, bananas, rice balls, boiled potatoes, and broth are all valid forms of carbohydrate fuel. In races lasting more than six hours, your gut typically needs real food — solid calories that digest differently from gels and are more sustainable over many hours.
Electrolytes and Hydration
Sweat contains sodium, potassium, and magnesium. In a race lasting 6 to 36 hours, electrolyte depletion is a real risk, especially in heat. Sodium is the most important variable to manage. Most ultra runners use a combination of electrolyte drink, salt capsules, and food with natural salt content throughout the race.
Drink to thirst rather than to a fixed schedule. Over-drinking can be as dangerous as under-drinking at ultra distances. Pale yellow urine is the target — clear usually means over-hydrated, dark amber means under-hydrated.
Practice Everything in Training
Every gel, food item, electrolyte product, and hydration strategy you plan to use on race day needs to be tested in training. Gut problems in a race are almost always preventable. Nothing new on race day is a hard rule.
To build a specific fueling plan for your target race distance, conditions, and sweat rate, use the Vert.run Nutrition Planner.
How Long Does an Ultramarathon Take?
Finish times vary enormously with distance, elevation, terrain, and the runner. These are realistic ranges for each common distance:
Distance | Typical Finish Time | Competitive Range | Standard Cutoff |
|---|---|---|---|
50k | 5–8 hours | 3:30–5:00 | 8–10 hours |
50-mile | 9–14 hours | 6–8 hours | 12–16 hours |
100k | 12–20 hours | 8–11 hours | 20–28 hours |
100-mile | 22–36 hours | 14–18 hours | 30–48 hours |
High elevation, technical terrain, and significant cumulative gain extend finish times. A 50k with 3,000 meters of climbing will take 1 to 2 hours longer than a flat 50k for most runners.
Your finish time also changes with heat. Hot conditions affect pace earlier in a race and compound fatigue — especially on longer courses where afternoon temperatures hit during the back half.
To estimate your specific finish time based on your fitness and the course profile, use the Vert.run Trail Race Time Predictor.
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Ultramarathon Gear: What You Actually Need
You do not need a lot of gear to run an ultra, but you need the right gear tested and dialed in before race day. Most trail ultras publish a mandatory gear list that is checked before the start. Showing up without required items means not starting.
Hydration pack or vest. A vest with soft flasks or a bladder is standard. Capacity depends on the distance between aid stations — some ultras have stations every 10 kilometers, others every 25+.
Trail running shoes. Lugged trail shoes with grip appropriate for the terrain and rock protection for technical courses. Road shoes are not suitable for most trail ultras. Test your race shoes on long training runs before the event.
Weather-appropriate layers. Races in mountain terrain or cold climates typically require a waterproof jacket, thermal layer, and gloves at minimum. Some require a full mandatory kit including survival blanket and emergency whistle.
Navigation. Some ultras require a GPS device with the course loaded, or a downloaded course on your phone. Check race rules well in advance.
Nutrition and electrolytes. Enough food and electrolytes to cover the distance between aid stations, plus a buffer.
For trail shoe selection, see the trail running shoes guide for beginners.
How to Choose Your First Ultra Race
Your first ultra should be chosen based on distance, terrain, and timing — not based on fame or how hard the race sounds.
Start with a well-organized, accessible event. Your first ultra should have clear cutoffs, well-stocked aid stations, a marked course, and reasonable logistics. This removes unnecessary variables on race day and lets you focus on running.
Match the course to your training. If you have been training on mostly flat terrain, do not pick a race with 4,000 meters of gain as your first. If you have been doing consistent hill work, a climbing-heavy course might suit you well. Read the course profile before committing.
Give yourself enough preparation time. Most first ultra training blocks run 16 to 24 weeks from a solid base. Count backward from the race date and confirm you have enough runway to build properly without rushing.
Pick a distance that is ambitious but achievable. Your first ultra should push you. It should not break you. The 50k is the right choice for most first-time ultra runners.
Ready to start training?
Every Vert.run training plan is designed by coaches who have worked with runners across all ultra distances and experience levels. Plans adapt to how your body responds week to week — adjusting volume, intensity, and recovery based on your progress.
If you want direct weekly guidance from a personal coach throughout your build, VertCoaching pairs you with a coach who reviews your training, sets targets, and answers your questions every week.
Ultramarathon Guide: Frequently Asked Questions
How long is an ultra marathon?
An ultra marathon is any footrace longer than a standard marathon — longer than 26.2 miles (42.195 km). The most common ultra marathon distances are 50k (31 miles), 50-mile, 100k (62 miles), and 100 miles. There is no single fixed ultra marathon distance — any race beyond the marathon qualifies.
What is an ultramarathon?
An ultramarathon is a race longer than the standard marathon distance of 26.2 miles (42.195 km). Most ultramarathons take place on trails and include significant elevation gain and descent. They range from 50 kilometers to multi-day events exceeding 100 miles. The sport is defined more by culture and self-reliance than by a specific distance.
How many miles is a 50k?
A 50k is approximately 31.07 miles (exactly 50 kilometers). It is the shortest and most common ultramarathon distance and the recommended starting point for most first-time ultra runners.
How long does an ultramarathon take?
Finish times depend on distance, terrain, elevation, heat, and the runner. A 50k typically takes 5 to 8 hours for most runners. A 100k takes 12 to 20 hours. A 100-mile race typically takes 22 to 36 hours. High elevation and technical terrain extend times significantly beyond flat-course estimates.
How do I start training for an ultramarathon?
Choose a distance and follow a structured training plan for that specific distance. You need a base of consistent running — able to run 90 minutes comfortably at an easy effort — and 16 to 24 weeks of build time. Focus on time-on-feet, hills, progressive long runs, and practicing your fueling strategy in training.
What should I eat during an ultramarathon?
Target 200 to 300 calories per hour, primarily from carbohydrates. Solid food becomes more important the longer the race — bananas, rice balls, boiled potatoes, broth, and sandwiches are all common at aid stations. The key rule: practice your exact fueling plan in training so nothing is new on race day.
Can a beginner run an ultramarathon?
Yes. Many runners complete their first ultra with fewer than two years of running experience. The key is choosing the right distance (the 50k is recommended for most beginners), building with a structured training plan, and committing to the long run work and terrain-specific preparation. Base fitness matters more than race experience.
How long should I train for my first ultramarathon?
Most runners need 16 to 24 weeks of structured training from a solid aerobic base. A 50k can work with 16 to 18 weeks. Longer distances — 100k and 100 miles — typically need 20 to 24 weeks of focused preparation. Rushing the build is the most common reason first-time ultra runners get injured before the start line.
─ Vert Pro · Vert Coaching: Designed and approved by expert coaches.
Trust the training.
Then trust race day.
