How long does it take to train for your first marathon?

The good news is that there’s no mystery to it: marathon training follows a fairly predictable pattern. The real factor isn’t your talent—it’s your starting point. In this guide, we’ll break down realistic scenarios based on your current fitness level, the prerequisites you need to meet before even starting a training plan, and how to choose your race date wisely while taking Québec’s seasons into account.

The short answer: 16 to 24 weeks

For most people, a marathon-specific training block lasts between 16 and 24 weeks—about four to six months. This is the timeframe used by the vast majority of serious training plans, and it’s no coincidence: it’s the time needed to gradually increase your running volume, get your body used to long runs, and recover between tough training blocks without rushing things.

But be careful—this timeframe assumes one important thing: that you already have a solid running foundation. The 16- to 24-week block is the home stretch. It’s not the absolute starting point for someone who has never run before. To truly understand how much time you’ll need, you first need to know where you’re starting from.

How long, depending on your starting point

The number of weeks of preparation depends heavily on your current fitness level. Here are the two main scenarios that most people fall into.

You’re already a regular runner

If you’ve been running three or four times a week for several months, comfortably clocking 25 to 30 km per week, and have already completed a 10K or a half-marathon, you’re in an excellent position. For you, a 16- to 20-week training plan is entirely realistic.

Your body has already developed the basic adaptations: tendons and muscles accustomed to impact, decent cardiovascular fitness, and a well-established routine. The marathon training block will simply build on this foundation by gradually increasing the length of your long runs. Our 20-week marathon program is designed specifically for this profile.

You’re a near-beginner

If you run infrequently, irregularly, or are starting practically from scratch, the honest answer is different: you’ll need more time, and you mustn’t rush things. Jumping straight into a 16-week marathon plan when you’re not yet running 25 km per week is an almost guaranteed recipe for injury.

The human body needs time to strengthen its tendons, ligaments, and bones. These structures adapt much more slowly than the cardiovascular system. You might have the stamina to run faster, but your joints won’t keep up at the same pace. It’s this mismatch that causes so many injuries among beginners who are in too much of a hurry.

For a near-beginner, a realistic plan looks like this:

• First, build a running foundation over 6 to 12 months, starting with short runs and alternating between walking and running.
• Progress to running continuously three times a week, then build up to 25 to 30 km per week.
• Complete a 10 km race, then ideally a half-marathon as an intermediate goal.
• Only then should you begin the 16- to 24-week marathon training block.

Add it all up, and you’ll often find it takes 12 to 18 months from your first day of running to the starting line of a marathon. That’s not discouraging—it’s simply realistic. If you’re at this stage, our guide to getting started with running is the best place to begin.

Prerequisites before starting a marathon training plan

No matter your background, there are specific milestones you need to reach before diving into a marathon training plan. They’re not meant to hold you back, but to protect you and ensure your training is enjoyable rather than a struggle to survive from week to week.

Before starting a marathon training plan, you should ideally:

• Be running 25 to 30 km per week comfortably, without persistent pain or excessive fatigue.
• Have been running regularly for at least 6 months, with a consistent routine of three runs per week.
• Have already completed an official 10 km race, and preferably a half-marathon.
• Be able to run a long run of 12 to 15 km without hitting the wall.
• Not be dealing with an active injury or recurring pain that flares up with every run.

If you check all these boxes, you’re ready to start a 16- to 20-week training block. If that’s not the case yet, take the time to build this foundation first. The marathon will still be there next year, and you’ll enjoy it infinitely more if you arrive prepared.

The risks of moving too fast

The temptation to speed up the process is real, especially when you’re motivated and a race is approaching. But rushing is the first-time marathoner’s biggest enemy. Here’s what happens when you increase your mileage too quickly.

• Overuse injuries: shin splints, Achilles tendinitis, iliotibial band syndrome, stress fractures. These injuries are almost always linked to increasing mileage too quickly.
• Chronic fatigue: A body that doesn’t have time to recover accumulates fatigue, which affects sleep, mood, and performance.
• Giving up: Many beginners who rush things get injured halfway through their training and have to stop everything—sometimes for good.

The best-known rule of thumb is to increase your weekly mileage by no more than about 10% from one week to the next, and to schedule a lighter week every three or four weeks to recover. It is precisely this gradual progression that explains why a true marathon training block takes so many weeks. You simply can’t compress this timeframe without paying the price.

How to choose your marathon date

Once you know how long your training period needs to be, choosing the right race becomes a simple calculation. The key is to plan backward from race day.

Plan backward from race day

Pick the marathon date that appeals to you and count back the number of weeks in your plan. For example, for an 18-week plan leading up to a marathon on September 20, your structured training should begin around mid-May. Then add a safety margin of two or three weeks to account for the unexpected: a cold, a week of vacation, or a minor injury that forces you to rest.

If, when working backward, you realize that the training block should start tomorrow morning but you’re not ready yet, that’s a clear sign: this race is too soon. Instead, aim for next year’s race or a marathon later in the season. It’s a thousand times better to postpone your goal than to get injured trying to make up for lost time.

Take Québec’s seasons into account

In Québec, the seasonal calendar imposes its own constraints, and it’s essential to take them into account when setting your date. Most marathons in the province take place in the spring or fall, which means that the bulk of the training block falls either at the end of winter or in the middle of summer.

• Fall marathon (September–October): The training block takes place during the summer. This is often the most popular choice, but you’ll have to deal with the heat and humidity during long runs in July and August. Plan your long runs for early in the morning.
• Spring Marathon (May–June): The training block spans the Québec winter. You’ll need to be prepared to run in the cold, on snow or ice, or to rely on the treadmill. Our guide to running in winter in Québec becomes invaluable.

For a first marathon, many runners find that an fall race is easier to train for, because you build your base in the spring when motivation is high and conditions are improving. But the best choice is still the one that fits your schedule and your tolerance for the conditions. You can explore marathons in Québec to find dates that work for you.

A concrete planning example

Let’s imagine Sophie, a beginner who has never run before and who decides in January that she wants to run a marathon. Here’s a realistic and conservative timeline for her:

• January through June: learn to run, alternating between walking and running, then progressing to continuous runs, up to 20 km per week.
• Summer: Build a solid foundation, increase mileage to 25–30 km per week, and run her first official 10 km race.
• Fall: Aim for a half-marathon as an intermediate goal.
• The following winter and spring: maintain her base throughout the winter, then begin the 18-week marathon training block.
• Fall of the second year: first marathon, about 20 months after the first day of running.

It may seem like a long time, but Sophie will be healthy, confident, and able to savor every kilometre. That’s exactly what we want for a first marathon. An experienced runner, on the other hand, could have skipped straight to the 18-week training block and aimed for a race as early as spring.

Conclusion

So, how long does it take to prepare for your first marathon? If you’re already a regular runner with a base of 25 to 30 km per week, plan on 16 to 24 weeks of specific training. If you’re starting from further back, plan on 12 to 18 months total to build your base before even thinking about the marathon training block. In any case, patience is your best ally: it protects you from injuries and makes the adventure infinitely more enjoyable. Choose your race date by planning backward, take Québec’s seasons into account, and meet the prerequisites before you get started. Ready to find the race that will become your goal? Take a look at the Québec race calendar to find the marathon that will get your heart racing.