How to Train for Your First Marathon
Training for your first marathon takes most people 16 to 20 weeks, built around a gradually lengthening long run, two or three supporting runs a week, and a genuine taper before race day. The single biggest factor separating runners who make it to the start line healthy from those who don't is how sensibly they increase their weekly load (Nielsen et al., 2012). Get that part right and the rest of the plan looks after itself.
How Long Does Marathon Training Actually Take?
Sixteen weeks is the commonly cited minimum for a first marathon, and 20 weeks gives you more breathing room. The extra month matters more than it sounds like it should. It buys you a spare week if you get sick, a slower ramp into your longest runs, and time to recover properly after your peak long run instead of rushing straight into taper.
If you're starting from a reasonable base, say you can already run 5 to 10 kilometres comfortably, 16 weeks is plenty. If you're closer to a beginner, 20 weeks or even longer gives your body more time to adapt to the cumulative load without forcing big jumps week to week.
How Much Base Mileage Do You Need Before You Start?
Before you begin a structured marathon block, most coaches suggest being able to run around 15 to 25 kilometres a week comfortably, across three or four sessions. This isn't a hard rule, but it matters because marathon training adds volume on top of whatever you're already doing. Starting a marathon plan from zero running background is where things tend to go wrong quickly.
If you're not there yet, spend four to six weeks simply building consistency: three runs a week, all easy, no long run longer than 8 to 10 kilometres. That groundwork makes the actual marathon block far more manageable.
How Should Your Long Run Progress Week to Week?
The long run is the heart of marathon training. It's the session that teaches your body to burn fuel efficiently, tolerates time on your feet, and builds the mental familiarity of running for hours rather than minutes.
A typical progression starts around 12 to 14 kilometres in week one of the block and builds toward a peak long run of 29 to 32 kilometres, usually reached two to three weeks before race day. That progression isn't linear. Most plans include a "step back" week every third or fourth week, where the long run drops by several kilometres to let your body absorb the load before pushing further.
Notice that the peak long run is deliberately short of the full 42.2 kilometres. Running the whole distance in training isn't necessary and often does more harm than good, since it adds a huge recovery cost right when you need to be tapering, not digging a hole.
What Is the 10% Rule, and When Should You Break It?
The 10% rule says you shouldn't increase your weekly running volume by more than about 10% from one week to the next. It's a useful guardrail, not a law of physics, and the research on training load is really pointing at a broader principle: sharp, sudden spikes in load are strongly associated with injury, regardless of the exact percentage (Nielsen et al., 2012).
In practice, this means resisting the urge to make big jumps after a good week. It also means the rule bends both ways. Step-back weeks, where you deliberately drop volume by 20 to 30%, aren't a violation of the principle, they're the same principle applied in reverse. The goal isn't rigid adherence to a number. It's avoiding the kind of abrupt, unplanned jump that catches your tendons and joints off guard.
How Much Rest Do You Actually Need?
More than most first-time marathoners think. A sensible week includes at least one full rest day, and often two, alongside a genuine easy day where the pace is comfortably slow rather than "easy" in name only.
Rest days aren't wasted time. They're when your muscles repair, your connective tissue strengthens, and your glycogen stores replenish. Skipping them to fit in extra kilometres tends to backfire, either through a nagging injury or through arriving at race day already running on empty. If your schedule only allows four running days a week, that's a completely viable marathon plan. Consistency across months matters far more than volume in any single week.
What Does a Taper Look Like?
The taper is the two to three week period before race day where volume drops sharply while intensity stays roughly the same. A common structure cuts volume by around 20% two weeks out and 40 to 60% in the final week, while keeping a handful of short, race-pace efforts to keep your legs sharp.
Tapering feels counterintuitive. You'll likely feel restless, maybe even a bit sluggish, and the temptation to sneak in one more long run is real. Resist it. The fitness you need for race day was built weeks ago. What the taper buys you is fresh legs and topped-up glycogen stores, both of which matter more on the day than anything you could add in the final fortnight.
When Does Fuelling and Hydration Start to Matter?
Once your long runs pass around 90 minutes, how you fuel and hydrate starts to genuinely affect how the session goes and how well you recover from it. The American College of Sports Medicine's position on nutrition and athletic performance is clear that carbohydrate intake during longer efforts supports performance and delays fatigue, particularly once you're running for extended periods (Thomas et al., 2016).
This isn't about anything complicated in the base-building phase. It's worth simply practising eating and drinking something during your longer weekend runs well before race day, so your gut is used to it and you're not experimenting for the first time in the marathon itself. Plenty of runners find a gel or two, alongside water and electrolytes, helps steady their energy through the second half of a long session. What matters most is finding what works for you well in advance, not on race morning.
Frequently Asked Questions
Can I train for a marathon on three runs a week? It's possible but harder to sustain the necessary long run progression safely. Four runs a week, including one long run, one easy run, and two moderate sessions, is a more common and reliable structure for first-timers.
What if I miss a week of training due to illness or travel? Don't try to make it up by cramming extra volume into the following week. Resume at a similar or slightly reduced load to where you left off and let the plan absorb the gap. One missed week rarely changes your race day outcome.
Do I need to run the full 42.2 kilometres before race day? No. Most plans peak at 29 to 32 kilometres in training. The taper and race day adrenaline typically carry runners through the remaining distance, and running the full marathon distance beforehand adds unnecessary injury risk and recovery cost.
How do I know if I'm increasing my training load too quickly? Persistent soreness that doesn't ease within a day or two, a pace that keeps slowing at the same effort, or disrupted sleep are common early warning signs. Training load spikes are one of the most consistent predictors of injury in runners (Nielsen et al., 2012), so when in doubt, hold volume steady rather than pushing on.
References
- Nielsen, R. O., Buist, I., Sørensen, H., Lind, M., & Rasmussen, S. (2012). Training errors and running related injuries: a systematic review. International Journal of Sports Physical Therapy, 7(1), 58-75.
- Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 48(3), 543-568.
Olly. Sunday Salt.
