When Should You Start Marathon Training? Your 2026 Autumn Countdown

How long should a marathon block actually be?

There is no single right answer, because the right length depends on where you are starting from. A marathon block is the focused stretch of training that takes you from your current fitness to the start line, and most plans fall somewhere between 12 and 20 weeks.

Here is the simple version, sorted by experience:

• True beginners (18 to 20 weeks). You are newer to running or you have never gone past 10k. You need time to build the habit, grow your weekly mileage slowly, and stay injury-free. Rushing this is the fastest way to get hurt.
• Runners with a base (about 16 weeks). You already run a few times a week and can comfortably cover 8 to 10k. Sixteen weeks gives you room to build distance, sharpen your pace, and taper properly.
• Experienced or time-crunched runners (12 to 14 weeks). You have done long races before and your body knows the work. A shorter block is realistic because you are topping up fitness, not building it from zero.

If you are honestly unsure which group you are in, round up. Extra weeks give you a buffer for the bad days, the missed sessions, and the niggles that every runner picks up along the way.

What "having a base" really means

People throw around the phrase "you need a base" without saying what it is. A base is simply your current running fitness: how often you run, how far you can go without falling apart, and how well your legs handle back-to-back days.

A rough guide: if you can already run 3 or 4 times a week and cover at least 8 to 10k in one go without it wrecking you, you have a base. If your runs are occasional, short, or you are coming back after a long break, treat yourself as a beginner and give yourself the longer block. There is no shame in it. It is the smart move.

How to count back from race day

This is the part most people get wrong. You do not start training on a date that feels nice. You start on the date that lands the end of your block exactly on race morning. So you count backwards.

Take your race day, subtract the number of weeks your block needs, and that is your start date. Using BMW Berlin on Sunday 27 September 2026 as the example, here is what the count-back looks like:

Look at the table and you can see the situation clearly. For Berlin, the 12 and 14 week start dates are right around now in late June. The 16, 18 and 20 week dates have already passed. If you have a base, you can still build a sensible block for Berlin starting this week. If you are a true beginner, the honest answer is that Berlin is tight, and a later autumn race will serve you far better.

The four phases of a marathon block

Whatever length you choose, a good block moves through the same four phases. Knowing them helps you see why the start date matters so much.

• Base. The early weeks. You build easy mileage and get your body used to running often. Most of this is gentle, conversational running.
• Build. The middle. Your long runs get longer and you add some faster work and marathon-pace efforts. This is where the real fitness is made.
• Peak. The biggest weeks of the block, with your longest long runs. This is the toughest stretch and the most rewarding.
• Taper. The final 2 to 3 weeks. You cut the volume right back so your legs arrive fresh. Resist the urge to keep grinding. The work is already done.

Skip or shrink any phase and something gives. Cut the base and you risk injury. Cut the taper and you arrive tired. The count-back exists so that every phase gets the time it needs.

Signs you should pick a later race instead of cramming

Sometimes the kindest thing you can do is move your goal. Consider a later autumn race if:

• The maths leaves you fewer weeks than your experience level needs, and the only way to fit it in is to skip the base.
• You are carrying a niggle or coming back from injury and need to build slowly.
• Your longest recent run is a long way short of where a block should begin.
• Fitting the training into your life would mean almost no rest days.

Berlin is the big late-September date, but autumn is generous. Chicago runs in October and New York lands in early November, both giving you noticeably more lead time. Starting now for one of those means a calm, well-built block rather than a frantic one. Arriving healthy and ready beats arriving on a deadline.

How Edge gets your block started today

The hardest part of any marathon block is often just starting one that fits your life. This is where Edge helps. When you sign up, a real coach builds your plan by hand within 24 hours, then Edge AI keeps adjusting it as you go. So you can decide to train today and have a structured, personal block in your hands tomorrow morning. No spreadsheets, no guesswork.

Life will not pause for your training, so Edge is built to flex around it. Use Flexi Swap to move a session to a day that actually works, and when your week needs a bigger rethink, just ask Edge AI and it reshapes your plan in under 30 seconds. You can also speak to our team of coaches when you want a human in the loop.

Throughout the block, progress tracking keeps an honest record of your pace, strength and consistency, so you can see the build happening week by week. General strength and mobility work is built into your plan to keep you durable, and your sessions sync across Strava, Garmin, Coros and Apple Watch. Edge is a hybrid running and strength app for 17,000+ UK members, and the whole idea is simple: making fitness feel good for everyone.

Frequently asked questions

What is the minimum time I need to train for a marathon?

For an experienced runner with a solid base, 12 weeks is a realistic minimum. Less than that and you are skipping phases your body needs. If you are newer to running, treat 16 to 20 weeks as your range rather than trying to squeeze it shorter.

Can a beginner do an autumn marathon?

Yes, with the right race and a sensible start. A true beginner needs 18 to 20 weeks, so from late June 2026 a late-September race like Berlin is very tight. A later autumn race in October or November gives you the full block you deserve, and that is the smarter way to start.

What if I miss a few weeks of training?

A missed session or two is normal and will not derail you. Do not try to cram the lost work back in. With Edge you can use Flexi Swap to shuffle sessions, or ask Edge AI to reshape your week in under 30 seconds. If you lose several weeks, it may be wiser to move to a later race than to rush back.

Do I really need a coach for a marathon?

You do not strictly need one, but a structured plan makes a real difference, especially for your first marathon. It takes the daily guesswork off your plate and helps you avoid the classic mistakes of doing too much too soon. With Edge a real coach builds your plan within 24 hours, then it adapts as you go, so you get that structure without the wait.

How do I know if I have a base or not?

If you already run 3 or 4 times a week and can cover 8 to 10k in one go without it wrecking you, you have a base and can aim for a 16 week block. If your running is occasional or you are returning after a break, treat yourself as a beginner and give yourself the longer runway.