Photo by Massimo Sartirana on Unsplash
You’re Actually Going to Run 42 Kilometres
It’s real now. You’ve decided to run a marathon, and suddenly 42.2 km (26.2 miles) feels simultaneously exciting and terrifying. You’re probably not an elite athlete. You might have never run more than 15 km (9 miles). You have a job, a family, maybe dodgy knees. And yet, you’re here.
The good news is that you don’t need to be fast or naturally gifted to finish a marathon. You need a plan that respects your life, builds gradually, and doesn’t assume you have hours to train every day. This is that plan.
A 16-week structure gives you enough time to build fitness properly without burning out. It’s long enough that you won’t panic-cram in the final weeks, but short enough to stay motivated and mentally committed. You’ll run four days a week, with one long run that progressively builds to 35–37 km (22–23 miles). That’s it. That’s your foundation.
How to Structure Your Week
Every single week follows the same pattern. This consistency is where the magic happens—your body adapts because it knows what’s coming.
| Day | Session | Pace | Notes |
|---|---|---|---|
| Monday | Rest or cross-training | — | Yoga, swimming, cycling. Light movement only. |
| Tuesday | Easy run | 5:30–6:00/km (8:50–9:50/mile) | Start at 5 km (3 miles) in week 1, build by 1 km every week. |
| Wednesday | Tempo or interval workout | 4:50–5:10/km (7:50–8:20/mile) | Structured effort, not a race. See section below. |
| Thursday | Easy run or rest | 5:30–6:00/km | 3–5 km depending on how you feel. |
| Friday | Rest | — | Sleep, recover, eat well. |
| Saturday | Long run | 5:45–6:15/km (9:15–10:00/mile) | The weekly hero session. See progression below. |
| Sunday | Rest or very easy 3 km | — | Complete rest is fine—listen to your body. |
This gives you 4 running days, 2–3 rest days, and a structure that’s repeatable. You’re running about 40–50 km (25–31 miles) per week by week 12, then tapering slightly in the final 4 weeks.
Your Long Run Progression (The Most Important Session)
The long run is where marathon readiness actually happens. This is where you teach your body to keep moving when it’s tired, where you test your fuelling strategy, and where you build the confidence to know you can cover the distance.
Here’s your progression week by week:
Weeks 1–4 (Base building):
– Week 1: 10 km (6 miles)
– Week 2: 12 km (7.5 miles)
– Week 3: 14 km (8.7 miles)
– Week 4: 10 km (6 miles) — recovery week, drop mileage
Weeks 5–8 (Building to half marathon distance):
– Week 5: 16 km (10 miles)
– Week 6: 18 km (11 miles)
– Week 7: 20 km (12.4 miles)
– Week 8: 14 km (8.7 miles) — recovery week
Weeks 9–12 (Beyond half marathon):
– Week 9: 22 km (13.7 miles)
– Week 10: 24 km (15 miles)
– Week 11: 26 km (16 miles)
– Week 12: 18 km (11 miles) — recovery week
Weeks 13–15 (Peak distance):
– Week 13: 28 km (17.4 miles)
– Week 14: 32 km (20 miles)
– Week 15: 35–37 km (22–23 miles) — your longest run
Week 16 (Taper):
– Week 16: 10 km (6 miles) easy, done mid-week. Then rest for 10 days before race day.
Notice the pattern: every fourth week is a recovery week where you drop mileage. This prevents overtraining and gives your body space to adapt. Long runs are done at a conversational pace—if you can’t speak in full sentences, you’re too fast.
Wednesday’s Workout: Tempo and Intervals
This is the day that builds your aerobic system. You’re not sprinting; you’re running at a pace you could hold in conversation, but just barely—around 5:00–5:15/km (8:00–8:25/mile) for most of these 16 weeks.
Weeks 1–6: Easy tempo work
– 5-minute warm-up easy jog
– 2–3 × 8-minute efforts at tempo pace (5:00–5:15/km / 8:00–8:25/mile), with 3-minute easy jogs between
– 5-minute cool-down easy jog
Weeks 7–12: Longer tempos
– 5-minute warm-up
– 1 × 15–20 minute effort at tempo pace
– 5-minute cool-down
Weeks 13–15: Shorter, faster repeats
– 5-minute warm-up
– 5–6 × 800m at 10K pace (4:45–5:00/km / 7:40–8:00/mile), with 90 seconds easy between
– 5-minute cool-down
Week 16: Rest week
– Easy 5 km run if you want to maintain feel for your legs
These sessions are hard but not brutal. You should finish them fatigued, not destroyed. The goal is teaching your body to run efficiently under aerobic stress—exactly what you’ll need at kilometre 30 of the marathon.
Fuel Your Long Runs
You won’t finish 42 km on empty calories. Start thinking about fuel by week 6, when your long runs hit 16 km (10 miles).
For any long run over 90 minutes, you need fuel during the run:
- Energy gels: Take one every 45 minutes, starting around 45 minutes in. A gel is roughly 20–25g carbs. Follow with water or sports drink.
- Sports drink: 500 ml (16 oz) every hour if you don’t like gels. It provides both carbs and hydration.
- Real food: Some runners do well with energy bars, date paste, or even a banana. Practise during training, not on race day.
- Hydration: Aim for 400–800 ml (13–27 oz) per hour depending on heat and sweat rate. Plain water is fine for runs under 90 minutes.
Start with one fuelling strategy and stick with it. Your gut needs to be trained just like your legs do. Most running gels and sports drinks contain similar carbohydrate ratios, so consistency matters more than the specific brand.
Recovery Weeks Are Not Failure Weeks
Every fourth week, your long run drops significantly, and your easy runs stay short. This feels counterintuitive—you might worry you’re losing fitness. You’re not. You’re consolidating it.
Recovery weeks give your body time to absorb the training stress and adapt. Skipping them almost guarantees injury or burnout by week 12. Embrace them. Use them to build strength, do yoga, sleep more. Your next big build will feel stronger because of it.
Avoid These Beginner Mistakes
Running all your easy runs at medium pace. Your easy pace should feel genuinely easy. If you’re breathing hard, you’re too fast. Easy runs should be boringly slow.
Skipping strength work. One session a week of glute bridges, single-leg calf raises, and core work prevents injuries. 15 minutes is enough.
Doing too much too fast. The 16-week plan is already optimised. Don’t add extra miles “just because.” Discipline is doing what’s planned, not what feels good.
Ignoring niggling pain. If something hurts, take a day off. A sore hip for 24 hours can become a 6-week injury if ignored.
Testing race-day gear on race day. New shoes, new shorts, new fuelling—never for the first time in a marathon. Use your long runs as testing ground.
The Honest Takeaway
A marathon is simply 16 weeks of showing up four times a week, running the plan, and trusting the process. There’s no secret. There’s no magic. You don’t need to be naturally fast. You just need consistency, patience, and the willingness to run slowly most of the time.
By week 15, you’ll have run 35–37 km in training. You’ll have felt genuinely terrible at some point and kept going anyway. You’ll know what your body needs in the final kilometres. And that’s all a marathon asks of you: to have done the work beforehand and then to apply it on race day.
Your future self—the one crossing that finish line—is being built right now, in week 1, with a slow easy run that feels pointless but isn’t. Trust the plan.
Next read: New to tempo runs? Here’s how to run them safely: /tempo-runs-what-they-are-and-why-they-work