How Long Is A 50k In Miles?


When you consider your running goals, you may be a beginner who is aiming to run their first 5-mile race.

If you are more experienced, you may be working towards a 10-mile race or a half-marathon—13 miles. Next up on the list is a marathon, which is just over 26 miles long.

If you have already run a marathon, you may be wondering what’s next. And you may have heard of ultra marathons. Generally, an ultra is 50 to 100 miles long, which could be intimidating – it’s almost twice the length of a marathon.

But technically, an ultra marathon is any distance longer than a marathon. And the next longest race distance after a marathon is the 50k.

Although kilometers is a metric measurement instead of imperial (what’s used in the USA) this is a common race distance that’s a logical next step after a marathon. It’s especially common in the trail-running world.

So how long is a 50k?

Well, a 5k is 3.1 miles, right? So just multiply by ten.

A race of 50 kilometers is 31 miles. If you’re paying attention to decimal places, it’s actually closer to 31.07 miles.

This is only slightly longer than a marathon, so it makes sense that it would be a logical next step once you have completed a marathon and are looking for a new distance challenge.

How long would it take to run this distance on a flat course?

The time it takes an individual to run a 50k depends on their training, the weather, what they ate the day before, and how they’re feeling on the day. But we can assume that most runners of the same skill level would usually fall into a similar category.

Runners who have a good deal of experience behind them and have built up the stamina should be able to run a 7:00 to 7:15 minute mile on a flat course. This equates to between 3:37 and 3:45 for 50k. But that’s pretty brisk.

Intermediate runners who can run an 8-minute mile and sustain their pace for the length of a 50k can finish it in 4:08. A 10-minute/mile runner who keeps their pace would make 5:10.

A speedy walker might take anywhere from 6:30 and up to finish a 50k race. For slower walkers, you can expect a 10-hour race.

Keep in mind that most 50ks you’ll find are trail races, and your pace on trails will be 25-50% slower than your pace on the road.

How long would it take to run it on a hilly or trail course?

It is generally much easier to sustain your pace when running on a flat course. But when the course incorporates hills, trails, or rough terrain, the time it takes to finish the course will increase.

Jack Daniels (no relation to the drink, or to the Whiskey Basin 60k!), a well-known running coach who wrote the popular Daniels Running Formula, has created a rule to help runners estimate how a hilly course will affect their running time.

According to Daniels’ rule, a runner will lose 12 to 15 seconds for every percent of incline on the course. On the other hand, every percent of decline will speed you up by 8 seconds.

For example, if the 50k course has just a single percent incline on each mile, you can lose 6 to 8 minutes on your final time. But if, for example, the race is in a loop and half of it is inclined and half is declined, you’ll only lose about a minute to a minute-and-a-half on your usual flat-course time.

Trail running is naturally slower than road running due to rougher terrain and more varied elevations. Runners tend to incorporate walking into steeper uphill sections as well.

In general terms, trails with lower elevations can add between 10 and 30 percent to your usual time, while higher-elevation courses can add 30 to 60 percent.

Trail ultras

You do get ultramarathons that are run on the road. But the majority of them are run on trails, and that is one of the most exciting features of ultras. If you are considering running an ultra — or even shorter distance trail race — you will need to get used to running on trails as opposed to on the road.

This will involve adjusting your training runs to spend more time on the trails than you do on the asphalt. You can do this gradually or more quickly, depending on how much time you have to train before your 50k race.

How much should I train for a 50k race?

Advanced runners can train for a 50k race in 2 to 3 months. Intermediate runners can get an adequate amount of training in around 6 months, while runners who are new to 50ks will need up to 9 months to prepare properly.

You should aim to run a total distance of between 40 kilometers (25 miles) and 100 kilometers (62 miles) per week. 25 miles is adequate when you’re beginning your training, but you should be hitting the 60-mile mark at least 2 or 3 weeks before your race.

You should be training 3 times a week at the minimum. 5 times is ideal, with 2 rest days. This will allow you sufficient rest, but you’ll be getting a high amount of training in and building up strength and endurance.

The different runs

You won’t be able to train the same way you did for your previous race if your upcoming race is a new type.

For example, if you last ran a flat marathon on the road and you are aiming for a trail ultra next, you’ll need to adjust your training to spend more time on the trails. If you know that your next course will have more hills, you will have to train in a hilly area to get used to the mechanics.

It is best to focus on long, slower runs rather than speed work.

You can certainly still incorporate speed work into your training, but only for about 15 percent. You want to be spending most of your training at 70 to 85 percent of your maximum heart rate, which is the endurance zone. Speedwork pushes you into a higher heart rate zone, which has different benefits but may be less useful for this kind of training.

If you run three times a week, it’s a good idea to vary your runs when you start. Do 1 long slow run, 1 faster and shorter run, and 1 mid-distance, moderate pace run. If you run more often, you can add a medium and a long run, or two medium and two longer depending on how you feel.

For example, if you’re starting off running 30 miles a week divided between 4 runs, you can do a shorter 5-mile run, 2 medium runs of 7.5 miles each, and a long run of 10 miles. This will increase week by week as you increase your distance and gain endurance.

The importance of long runs

An ultra-marathon is long! Even if you aren’t doing a 50 or 100-mile run, 31 miles is a significant distance. Incorporating long runs into your training is essential to build the necessary endurance.

These long runs will be the hardest part of your training, but they are the most important. This is where mental fatigue and physical fatigue will set in, and you will need to learn how best to nourish and nurture your body to be able to power through the distance as comfortably as possible.

Because it may take some experimenting, it’s advisable to make your long run the main focus of your training. Increase the mileage slowly week by week, making sure you’re constantly improving.


While nutrition is important to run your best race, there’s no need to go crazy and change your whole diet—unless you are eating a diet mostly of fast food.

If you are already eating healthy, there’s no need for drastic changes. It’s a good idea to increase your carbohydrate intake by 10 or 20 percent, but make sure that you aren’t increasing your calorie intake. You will simply need to tweak your food intake a bit so that you are eating more carbs and slightly less protein and fat.

You will gain benefits from carbo-loading from about a week before the race. The purpose of carbo-loading is to build up glycogen stores in the muscles so that when you’re in the middle of a long race and your body needs extra energy, it can access it easily.

This definitely doesn’t mean eating a lot of processed hi-carb food without taking note of nutrients and calories. On carb-heavy days, aim for 70 to 80 percent of your food intake to be carbohydrates. They should be healthy carbs, but it’s best that they are low-sugar and low-fiber.

Pasta is a great choice, as are vegetables. Fruits can be high in sugar, so be careful which ones you choose.

You should do a mini carbo-load for about 2 days before your long run every week. This will provide the energy you need to see you through the longer sessions. Hydration is also extremely important. It’s a good idea to invest in a hydration pack for longer runs so that you don’t have to worry about carrying bottles of water around with you.

Strength training

Including strength training in your routine can build muscle and increase your strength, helping your muscles stay strong for longer before they fatigue.

If you can add one or two 20-40 minute strength-training sessions every week, you can build extra strength. Focus on legs and core, but don’t neglect the upper body.

It’s advised that you do low to medium-intensity workouts so that you don’t fatigue yourself and struggle with your running. Aim for 50 to 70 percent of your maximum effort.


Don’t forget that recovery is as important as your training. All of your hard work will go to waste if you aren’t getting good enough rest and recovery. As the miles pile up for ultra training, you’ll feel the increasing need for proper recovery. Listen to your body.

This is two-fold. Sleep is when your body heals, so you need to be getting your 8 hours a night in order to keep your body strong. Muscle recovery is the other factor. Avoid fatiguing your muscles in your cross-training, and make sure you warm up and cool down properly before every run.

It may be wise to invest in a foam roller so that you can roll out tense muscles when you need to. Compression gear is especially popular with ultra runners, and could be helpful. You can also do one or two yoga sessions per week.


Enjoying your experience is the most important part of running. It is why we run!

Training can be tough, and there’s always bound to be a difficulty along the way, whether it’s physical aches and pains or breaking through a mental barrier.

Training for a 50k is a long process. While race day is important, and it’s what you’re working towards, you need to enjoy your training process too. After all, race day is only one day, but training is going to take you months!

Running a great race is a bonus, and there’s no feeling quite like reaching your goal. But take pride in yourself, keep your expectations realistic, and above all, enjoy the whole process!

Photo of author


Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.