How long do you need to train for a marathon?
If you already run a few times a week, a focused block of around four to five months is a sensible target. If you are starting from nothing, spend the first two months simply running easily and consistently before the marathon plan begins. I ran mine at 23 off about three miles a week and finished in a medical tent — it is possible and it is a bad idea.
Starting from nothing
Two months of easy running, four or five times a week, without missing sessions, before you think about a plan. Consistency at low effort builds more than heroics at high effort, and it is the only thing that reliably keeps you uninjured.
Starting from some base
Four to five months is comfortable. Gradually lengthen one weekend run, keep everything else easy, add a little intensity once a week if you enjoy it, and take an easy week roughly every fourth.
What rushing actually costs
Not a slower time — an injury in week six, or a finish so unpleasant you never run again. My first marathon was the second version of that, and it took a long time to want to run properly afterwards.
The taper
Cut the volume in the last two weeks and resist the urge to prove your fitness. The training is already done; all you can do in that fortnight is damage it.
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Get my 21 SAS reserve selection prep guide
What the stages are, what I was training to before I applied, and how I'd build the twelve weeks before a selection weekend. Written from my own application, free, no pitch.