What Should Your Longest Run Be In Marathon Training?

You’ve signed up for a marathon and you know you’re going to have to run 26.2 miles or 42.2 km. But how far should your longest training run be before a marathon?

WHY LONG RUNS ARE IMPORTANT FOR MARATHON TRAINING

Every week in your marathon training block you’ll have a long run, which most people run on Saturday or Sunday. It’s arguably the most important run of the week for marathon training and for most runners the longest run they’ll do when marathon training will be 16-22 miles/25-35km or 2.5-3 hours (here’s a handy guide for mile to km conversions if you need one).

As your training progresses, the long runs gradually get longer, with the longest of them all being run three or four weeks before your race. There are many reasons why long runs are so important to marathon training. 

• They help you get more comfortable with running for long distances. By adding a little more time or distance each week, you slowly build up your cardiovascular fitness as well as your muscular tolerance to running further. It’s important to gradually increase the distance each week to reduce the risk of injury.
• Long runs allow you to properly practise your race nutrition, so you can get used to drinking while running, taking gels or energy chews, and also trying the best pre-run breakfast for you. You can also practise wearing all your race day kit, including your shoes.
• Long runs help us work on the mental strength needed to run a marathon. Those longer runs are challenging, so if you can get through them in training, you’re better prepared and more confident for race day. 

While your long runs are very important, they are not the only run in your week, and the progress of marathon training is a cumulative process, where every run ultimately adds to your fitness. You need to have a balance of easy running, some faster runs and your long run each week.

But there can be some negatives to long runs as they are challenging and can leave you fatigued for the next week’s training. For your longest run you want to ensure you have good nutrition before, during and after, and allow enough rest and recovery time afterwards – we’ve got some top long run tips at the end of this piece. 

WHAT DOES A MARATHON TRAINING LONG RUN LOOK LIKE?

For most of your training, your long runs will be run at a relatively easy pace that you can maintain for the duration of that run. Especially early in your training block, the main aim will be to complete the distance or duration, without any focus on pace.

If it’s your first marathon or you don’t have any specific time goals in the race, then all of your long runs will be at this intensity as the most important thing is that you complete the run at whatever pace is comfortable for you. 

If you’re chasing a certain time, then as the race gets closer you’ll want to think about doing some marathon-specific long runs. 

For example, you might have a 20 mile/32km run. You could do a ‘negative split’ long run by doing the first 10-14 miles (16-23km) at a steady pace and the rest at race pace – this prepares your body to run at goal pace while fatigued. Or you could do a run that’s 10 x 2 miles (3km) alternating between a steady pace and marathon pace.

HOW LONG ARE THE LONGEST LONG RUNS IN MARATHON TRAINING

Look at dozens of training plans and you’ll see lots of different distances for the peak long run, but for most marathon training plans the longest run will be 16-22 miles (or 2.5-3 hours), which you’ll run three or four weeks before your marathon. 

But it’s an individual thing for runners and the more marathons you do, the more you know what works best for you. Some runners like to do a few 16 mile long runs, while others favour running six or more 20+ mile runs to feel prepared. If it’s your first marathon, then aim to build to a longest training run of three hours.

Asking around The Running Channel office, most people would do 2-4 long runs around 18.5 miles/30km, and some would also do one slightly longer long run to about 22 miles/35km. 

A couple of the faster marathoners in the team would run around 24 miles/38km as their longest run, with at least three or four runs over 20 miles.

It’s likely that your longest long run will depend on your goal time (though this will all depend on what you are comfortable running and there are exceptions – some 2:30 runners will only do a 25km run and some 6:00 runners will do 35km). 

• Sub 2:30/elite marathoner: 22-25 miles / 35-40km
• Sub 3:00 marathoner: 20-24 miles / 32-39km
• Sub 4:00 marathoner: 16-20 miles / 26-32km
• Sub 5:00 marathoner: 16-19 miles / 26-30km
• 6:00+ marathoner: 14-16 miles / 22-26km

DO YOU NEED TO RUN AT LEAST 20 MILES AS A LONG RUN IN MARATHON TRAINING?

For many people, 20 miles/32km will be the longest run they see in their marathon plan.

While 20 miles is a nice psychological barrier to get up to in training, it may be too far for some runners and it could increase your risk of injury or lower your ability to recover properly.

In general, you won’t want to do a long run which lasts much more than three hours (or if you do run further then you’ll want to plan for additional recovery time). If you are aiming to run your marathon in five or six hours, then that might mean a 15 mile/24km long run is the furthest you go and that’s absolutely fine.

If your longest training run will be 14-16 miles, then try to do this distance 2-3 times during your training, and also do your best to be running four times per week in total to build up your overall running volume. Like we’ve said, marathon training is not just about your one weekly long run, it’s about everything you do and building up your general fitness and strength.

WOULD YOU EVER RUN 26 MILES WHEN TRAINING FOR A MARATHON?

We wouldn’t advise this for inexperienced runners. Completing a 26 mile run is hard on the body and requires good strength and a priority on recovery, which often means that you have to miss one or two quality runs just to add a few extra miles to a long run.

More experienced runners and elites may choose to do a long run that is very close to a marathon, though they won’t run the whole distance at race intensity to ensure they are able to recover properly to maintain their training in the following week.

If you’re a runner that feels like they need to run all or most of the distance before the race, then just follow some of the tips below, and plan to have additional rest and recovery time afterwards.

TOP LONG RUN TIPS

As you get closer to race day, the final few long runs should be dress rehearsals for your marathon, and you should think about:

• Run a route or terrain similar to (or more challenging than) your race course. If it’s a hilly marathon, then find a route with similar hills. If it’s flat, then if you run a route with some hills on it then race day will feel easier in comparison.
• Carb-load and get well hydrated in the day or two before your long run to practise the food and drink that works for you before running. Then practise your pre-run breakfast and eating it with similar timings to your race (so if you start your race at 9am, get up to eat your breakfast around 6am).
• Try out your race nutrition, so carry water and the number of gels you expect to take during the marathon.
• Do at least one run wearing the full kit you plan on using in the marathon, just in case you find that something rubs when you run.

Not all long runs will go well, and it may be there you struggle to cover the distance, or find it challenging to take on your race nutrition. Don’t worry. We use long runs to learn and to improve for next time. Recover well, figure out what the problem was, and try again next week.

The race experience is also very different to training. You get to the start line having tapered, so you should feel fresher, and you’ll have people all around you cheering you on which helps carry you those extra miles.

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Here’s Sarah taking you along with her on her longest run before the 2024 TCS London Marathon