Categories / Running & athletics
Marathon Training
16-20 week build to 42 km.
How to start
Build a base first: you should already run regularly for several months and be comfortable with about 15 to 20 km. Marathon plans run 16 to 20 weeks with four or five runs a week.
How to progress
Raise the long run steadily, with an easier week every fourth week, peak at about 30 to 32 km three weeks before the race, then taper.
What the evidence says
Evidence: limited
A 2025 JAMA study of 29.3 million US marathon and half-marathon finishers recorded 176 cardiac arrests, an overall rate of 0.54 per 100,000, higher in the full marathon (1.04 per 100,000) and in men. Deaths from cardiac causes fell compared with 2000 to 2009. Training-injury research is mixed, and we found no trials comparing marathon plans.
Take care: A marathon is a big physical demand. See a GP first if you have a heart condition, high blood pressure or chest symptoms, and stop if you feel chest pain, faintness or unusual breathlessness.
Sources
12-week starter plan
This is the first 12 weeks of a 16 to 20 week build, for someone who already runs 15 km comfortably. Add the final weeks and a taper before race day. Most runs are easy.
Tick each week as you finish it; your ticks are saved on this device only. Repeat a week if it felt hard. Weeks 4, 8 and 12 hold steady so you can settle. This is a general plan, not medical advice.
Add reminders to your calendar
Pick your days and time. You will download a calendar file that adds 12 weeks of reminders to Google, Apple or Outlook calendar.
Calories and weekly minutes
Enter your details for a rough estimate. Based on about 9.5 METs (Steady distance running (about 6 mph)). Real figures vary by 20% or more between people.
Tips and common mistakes
Tips
- Run most miles slowly and keep the long run easy.
- Practise drinking and fuelling on long runs.
- Plan recovery weeks and sleep as seriously as the runs.
Common mistakes
- Skipping the taper.
- Running too fast on the easy days.
- Starting the marathon too fast.
Kit and cost
Moderate to high Approximate UK prices.
- Running shoes (about £80 to £160), more than one pair
- A running watch (about £100 to £400), optional
- Energy gels or chews and a race belt
- Race entry (about £50 to £120)
Frequently asked questions
How long does it take to train for a marathon?
About 16 to 20 weeks for someone who already runs regularly. First-timers usually need several months of base running before that.
Is a marathon dangerous?
Serious cardiac events during marathons are rare but they do happen. In a 2025 US study, about 1 in 100,000 marathon finishers had a cardiac arrest.
How far is the longest training run?
Many plans peak at about 30 to 32 km, three weeks before the race.
Can I walk some of it?
Yes. Many people use run-walk intervals in a marathon, and most races allow it.
Good for: Endurance Heart & fitness
Compare with similar options
| Marathon Training | Hill Repeats | Ultra Running | Interval Running (Fartlek) | |
|---|---|---|---|---|
| Typical session | 75 min × 5/wk | 40 min × 1/wk | 120 min × 5/wk | 40 min × 2/wk |
| Effort | ●●●●● | ●●●●● | ●●●●● | ●●●●○ |
| Cost | Moderate cost | Free | Moderate cost | Low cost |
| Equipment | No equipment | No equipment | Basic kit | No equipment |
| Impact | High impact | High impact | High impact | High impact |
| Fitness needed | Good fitness | Good fitness | High fitness | Moderate fitness |
| Evidence | limited | limited | limited | moderate |