Most people asking how many miles a week they need for a marathon are really asking two things. Am I doing enough to get round? And am I doing so much that I'll get hurt before I get there?
The honest answer is that there isn't one number. But there is a sensible range for your goal, a safe way to build towards it, and a few things that matter more than the headline figure. I've coached well over a thousand runners, and the mileage question comes up with almost every one of them, so here's how I think about it.
The short answer
For most people training for a spring marathon, peak weeks somewhere between 30 and 50 miles (roughly 50 to 80 km) will get the job done well. First-timers aiming to finish can do it on less. Runners chasing sub 3 usually need more.
What matters just as much is where you start, how quickly you build, and how many of those miles are easy. A steady 35 miles a week that you can repeat for three months beats a heroic 55 that lasts a fortnight.
What the research says about weekly mileage
The evidence is pretty consistent on one thing... more running tends to go with faster marathons.
A meta-analysis pulling together 85 studies and 137 groups of marathon runners found that average weekly distance, the number of runs per week, the biggest week, the number of runs of 32 km or more and hours of running per week were all linked with faster finish times (Doherty et al., Journal of Science and Medicine in Sport, 2020).
A much smaller study of 22 runners, finishing between about 2:47 and 3:36, found that average weekly distance and average training pace over the last eight weeks before the race were the two best predictors of marathon time (Tanda, Journal of Human Sport and Exercise, 2011). The relationship flattens as the miles go up, so each extra 10 km a week buys you a little less than the last.
Two caveats, because they matter. These are observational studies, so part of the link is simply that fitter, more experienced runners run more. And neither study tells you what your body can absorb right now. That's where the coaching comes in.
How many miles a week for your marathon goal
These are my rules of thumb for peak weeks, not laws. They assume you've built up to them over months, and they assume most of the running is easy.
- First marathon, aiming to finish: about 20 to 35 miles a week (30 to 55 km), usually over three or four runs.
- Sub 4 hours: about 30 to 45 miles a week (50 to 70 km), over four or five runs.
- Sub 3:30: about 40 to 55 miles a week (65 to 90 km), over five runs or so.
- Sub 3 hours: about 50 to 70 miles a week (80 to 110 km), usually five to seven runs.
If you're chasing a London Good for Age time, the band you're in will push you towards the upper end of these ranges. I've written about the standards in London Marathon Good for Age times.
Miles or minutes?
I say this all the time... the body doesn't know what a mile is. It knows time and effort.
A 4:30 marathoner and a 3:00 marathoner running 40 miles a week are doing very different amounts of work. The slower runner is on their feet for a lot longer. So if you're newer to running or you're on the slower side, it can make more sense to plan in time. Five to six hours of running a week at peak is plenty for many first-timers, and it stops you chasing a mileage figure built for someone quicker.
How fast to build your mileage
In my experience, this is where most injuries come from. It is usually the size of the jump that does the damage, rather than the total.
The famous "10% rule" is a cautious guide rather than something proven. In a study of 874 novice runners, those who increased their weekly distance by more than 30% over a two-week period had a higher rate of overuse injuries like runner's knee, IT band pain and shin splints than those who increased by less than 10% (Nielsen et al., JOSPT, 2014). The difference for all injuries combined wasn't statistically significant, so treat it as a sensible guardrail rather than a magic number.
What I do with the runners I coach:
- Build from what you've actually been running for the last four to six weeks, not from your best ever month.
- Add a little at a time. A couple of miles a week, or a few extra minutes on two or three runs, is enough.
- Drop back every third or fourth week. A lighter week lets the work land. Then build again.
- Change one thing at a time. If the long run is growing, don't add a new speed session the same week.
- Treat niggles as information. A sore spot that changes how you run means a lighter few days, not pushing through.
Where the miles should go
Big weekly numbers only help if you can recover from them, and that means most of the running needs to be genuinely easy. Conversational, a bit boring, the kind of pace where you finish feeling like you could do it again. If you want the why behind that, I've written about the benefits of easy running.
A rough shape for a peak week:
- One long run, usually no more than about a third of your weekly total. How long it should be is its own question, covered in how far your longest marathon training run should be.
- One quality session, such as threshold reps or marathon-pace work.
- Everything else easy, with strides now and then if you're feeling fresh.
Spreading the same mileage over more runs is often kinder on the legs than cramming it into three big days. Fifteen miles across three runs and fifteen miles across two are not the same week.
Older runners and busy weeks
If you're in your 50s or 60s, or you've got work and family pulling on your time, the ranges above still apply, but you may need to sit at the lower end and recover a little longer between harder days. Plenty of runners do brilliantly on four runs a week plus some strength work and the odd bike session. I've written more on this in coaching older athletes.
The best mileage is the mileage you can keep turning up for. Consistency over months beats any single big week.
If you're starting a spring build now
November is a good time to be asking this. If you're racing London, Manchester or Brighton in April, you've got time to build your base gently over winter before the specific work starts in the new year.
A simple way to start:
- Work out your average weekly running over the last month. That's your starting point.
- Pick a realistic peak from the ranges above for your goal.
- Count the weeks between now and about three weeks before race day, and check you can get from one to the other with small steps and regular lighter weeks.
- If the gap is too big, change the goal or the peak. Don't squeeze the build.
For the full week-by-week structure, have a look at my marathon training plan guide.
FAQs
Is 20 miles a week enough to run a marathon?
It can be enough to finish, especially if you've been running for a while and your long run builds properly. It's usually not enough to run to your potential, and the last few miles on race day will likely be hard work.
What's the minimum weekly mileage for marathon training?
There isn't an agreed minimum. For a first marathon I'd want most people to be comfortably running at least three times a week and peaking somewhere in the 20 to 35 mile range before they toe the line.
When should my biggest week be?
Usually about three to four weeks before race day, before the taper starts.
Do warm-ups and cool-downs count?
Yes. It's all running, and your legs count every step of it.
Should I count miles or kilometres?
Whichever you'll actually track. The ranges above are given in both.
Want a coach to set the numbers for you?
You can do all of this yourself with the steps above. If you'd rather have someone set your weekly mileage around your history, your goal and your diary, and adjust it when life gets in the way, that's what we do at Maximum Mileage. See the coaching options.
Header photo: Marathon runners on Hull Road by DS Pugh, CC BY-SA 2.0, via Wikimedia Commons.
