An ultra marathon is any race longer than 26.2 miles, which covers an enormous range: a 50K on a canal towpath and a 268-mile winter crossing of the Pennines are both ultras, and they have almost nothing in common.
Across the 212 ultras listed on this site, the median distance is 43 miles and the range runs from 26.5 to 268. Seventy-five of them are under 35 miles. That bottom band is where a first ultra belongs, and this guide is about how to choose one, how it differs from a marathon, and how to get to the finish.
Start at 50K
50K is 31.1 miles — about five miles beyond a marathon. That sounds like a modest step and it is, which is exactly the point: it lets you meet everything that is genuinely different about ultra running without also meeting a distance you have no reference for.
| Band | How many on this site | What it asks of you |
|---|---|---|
| Under 35 miles (50K-ish) | 75 | A marathon plus a bit, on terrain. The right first ultra. |
| 35-55 miles | 61 | A genuine step up. Night-time is unlikely but fuelling becomes decisive. |
| 56-80 miles (100K-ish) | 30 | Likely to involve darkness, crew or drop bags, and real sleep deprivation for slower runners. |
| 81-110 miles (100 miles) | 24 | A different sport. Cut-offs of 28-36 hours are typical. |
| Over 110 miles | 11 | Multi-day. Not a distance you build to in one season. |
The jump from 50K to 100 miles is not a matter of degree. A hundred-miler means a full night of running, a crew or a drop-bag strategy, sleep management and a level of foot care that has no marathon equivalent. Everything below assumes you are starting at the bottom band, which is where almost everyone should.
Read the cut-off before anything else
As with a first marathon, the cut-off is the number that decides whether a race is a sensible first attempt. Ultra cut-offs are usually generous, but not always, and the variation between similar-distance races is large.
| Race | Distance | Cut-off |
|---|---|---|
| Chiltern Ridge Classic 50K | 31.1 miles | 9 hours |
| Hurtwood 50K | 31.1 miles | Around 10 hours |
| Boudicca Way 50K Ultra | 31.1 miles | 10 hours |
| Tiree Ultramarathon | 35 miles | 10 hours |
| The Cerne Giant | 30 miles | 11 hours |
| Dartmoor Discovery | 32.5 miles | 6 hours 45 minutes |
Look at the last row
Dartmoor Discovery is 32.5 miles with a 6 hour 45 cut-off — tighter, per mile, than most road marathons. Two races at effectively the same distance can be a relaxed day out and a hard qualifying standard. Never assume 'ultra' means 'generous'; read the specific number.
Also check for intermediate cut-offs. Many ultras enforce checkpoint times as well as an overall limit, and a race can end for you at 20 miles even though the overall cut-off looked comfortable.
The three things that actually change
1. Walking is a strategy, not a failure
This is the largest mental adjustment and the one that most determines whether a first ultra goes well. In a marathon, walking usually means something has gone wrong. In an ultra, walking the climbs from the start is what experienced runners do deliberately, and it is faster over the distance than running them and paying for it later.
The standard approach is to run the flats and downhills, walk anything meaningfully uphill, and eat while walking. Adopt it from mile one rather than from the point where you have no choice — a first-timer who runs every hill for fifteen miles is making a decision about miles twenty-five to thirty-one whether they realise it or not.
2. Real food replaces gels
Six to ten hours is long enough that gels alone stop working, both because your stomach tires of them and because you need more total calories than a gel strategy comfortably delivers. Ultra aid stations are famously different from road-race ones: sandwiches, crisps, cake, sausage rolls, boiled potatoes, sweets, flat cola.
- Practise eating on long training runs. Your gut is trainable, and race day is the wrong place to find out what it tolerates.
- Eat early and eat regularly — well before you feel like you need to. Once you are behind on calories in an ultra, catching up is very difficult.
- Take salt as well as calories, particularly in warm weather over that many hours.
- Carry some food you know works, regardless of what the aid stations promise.
3. You carry your own kit
Most trail ultras have a mandatory kit list, and it is checked. Typical items include a waterproof jacket with taped seams, a hat and gloves, a head torch, a foil blanket, a whistle, a charged phone, a mapped route or GPS, and your own cup — many races are cupless to avoid waste.
This changes training as well as race day. You need to have run long in the pack you will race in, with the weight you will actually carry, or you will discover a chafing problem at mile eighteen that you cannot solve.
Terrain, and why pace stops meaning anything
Most ultras are off-road, and trail pace bears very little relationship to road pace. A runner who comfortably holds nine-minute miles on tarmac may average fourteen or more on a technical trail with climbing, and there is nothing wrong with that.
This is why ultra runners talk in hours rather than in pace. The useful planning number is not minutes per mile but how long you expect to be out — and that number is what you fuel, hydrate and pace against.
Where elevation is published it is worth taking seriously. On this site the extremes are stark: the Dragon's Back Race covers 236 miles with 57,086ft of ascent, and the Montane Spine races cover 268 miles with 35,210ft. Those are not first ultras, but they illustrate that distance alone tells you very little.
Training for a first ultra
If you have run a marathon, you are most of the way there. The changes are ones of emphasis rather than a different sport.
- Back-to-back long runs — a long run on Saturday and a moderately long one on Sunday — teach you to run on tired legs, which is the specific quality an ultra demands. This is the single most useful ultra-specific session.
- Train on terrain like the race. Road-trained legs on a technical descent at mile twenty-five is where ankles go.
- Practise the whole system on long runs: pack, food, poles if you will use them, shoes, socks. Nothing new on race day, extended to everything rather than just shoes.
- Time on feet matters more than mileage. A five-hour hilly trail run is better ultra preparation than a faster twenty-two-mile road run.
- Walk in training deliberately, including uphill walking with purpose. It is a skill and it is trainable.
- You do not need to run the full distance in training. Most 50K plans peak somewhere around 20-26 miles.
Getting to the finish
- 1 Start slower than feels right, by a wide margin. In an ultra the cost of starting too fast is not a fade, it is a death march.
- 2 Walk the hills from the beginning, not from the point of desperation.
- 3 Eat something at every aid station, whether or not you feel like it. Set a timer if you need to.
- 4 Deal with feet early. A hot spot at fifteen miles is a two-minute fix; at twenty-five miles it is a race-ending blister.
- 5 Expect at least one genuinely bad patch, and expect it to pass. Almost everybody has one, and almost everybody who eats, drinks and keeps moving comes out the other side.
- 6 Break the race into aid stations rather than thinking about the distance. Thirty-one miles is daunting; six miles to the next checkpoint is not.
The thing everyone says afterwards
The physical difficulty of a first 50K is usually less than people fear and the mental difficulty is different from what they expect. It is rarely one moment of agony; it is a long stretch of ordinary discomfort that you have to keep choosing to continue through. That is a skill, and it improves with practice like any other.
The part that surprises marathon runners
Ultra running is markedly more sociable than road racing. Fields are small, you spend hours next to the same people, and it is normal to run with strangers for a whole section and never see them again. Aid stations are staffed by volunteers who will feed you and ask how you are and mean it.
Practically, this makes it one of the easier disciplines to get into on your own — but it is easier still with company, and a first ultra is a much better day with someone who has done one before. Finding that person is worth more than any piece of kit. If you do not have one, a Verus profile is one way to put a first ultra on the record as a stated goal, with the date, so people who are doing the same thing can find you.