Ethan BrooksBy Ethan Brooks

Updated November 2026

A first full marathon training plan gives you a structured path from your current fitness to 26.2 miles, usually over 16 to 20 weeks. This guide explains how to pick the right plan length, build your weekly schedule, and avoid the mistakes that send most first-timers to the injury list. By the end, you will know what your week should look like and how to adjust it as you go.

Choose a Plan Length and Starting Mileage

Most beginner marathon plans run 16 to 20 weeks. Use the longer end if you are currently running less than 15 miles per week, or if you have never completed a race longer than 10K. Before you start, you should be able to run comfortably for 30 minutes at a time, three to four days a week.

Shopping for one? See our guide: Runner's World First Marathon Training Plan: 7 Best Picks for Beginners (2026).

Your peak long run for a first marathon typically lands between 18 and 20 miles, three to four weeks before race day. Plans that go much higher tend to add injury risk without much payoff for a first-timer.

Build a Weekly Structure

A beginner week usually includes four components. Each one has a different job, and you should not skip any of them.

  1. One long run on the weekend, starting around 6 to 8 miles and increasing by about 1 mile per week, with a cutback every third or fourth week.
  2. Two easy runs at a conversational pace, 2 to 5 miles each.
  3. One quality session, such as tempo intervals or hill repeats, kept short and controlled.
  4. One or two rest days, including at least one full day off from running.

Keep total weekly mileage increases to about 10 percent or less. A typical beginner plan might move from 15 miles in week one to around 40 miles at peak.

Plan Your Fueling and Recovery

Your long runs are where you practice fueling. Start taking gels or chews around the 60-minute mark, then experiment with timing and brands in training. Never try a new product for the first time on race day.

Sleep, hydration and easy days do as much work as the hard ones. If your resting heart rate climbs, your legs feel heavy for several days, or a pain sharpens instead of fading, back off and consult a doctor or sports medicine professional before pushing through.

Essential Items to Have Before Week One

  • A calendar or training log to track weekly mileage
  • Running shoes fitted at a specialty store, with at least 100 miles of wear left
  • A race-day fueling plan tested on long runs
  • Entry confirmed for a race at least 16 weeks out
  • A basic strength routine two days per week

Common Mistakes

  • Running every day at the same moderate pace, which leaves you tired and no faster.
  • Jumping straight to a 20-miler without building up to it.
  • Ignoring pain that changes your stride or lasts more than a few days.
  • Skipping the taper, then trying to cram in extra miles.
  • Wearing brand-new shoes or clothing on race day.
  • Running shoes: A well-fitting cushioned pair reduces the impact load across hundreds of miles. View on Amazon
  • Hydration belt: Carrying water on long runs helps you practice drinking at a steady rate. View on Amazon
  • Foam roller: Light self-massage can ease tight calves and quads between sessions. View on Amazon

FAQ

How many weeks do I need to train for a first marathon?

Most beginners need 16 to 20 weeks. If you are already running regularly and comfortable with 10-mile weeks, the shorter end can work.

How many days per week should I run as a beginner?

Three to four running days per week is typical, with one long run and at least one full rest day. Cross-training can supplement but should not replace the long run.

What if I miss a week of training?

Resume at the mileage you were doing two weeks earlier rather than picking up where you left off. Do not try to make up missed miles.

Conclusion

A solid first full marathon training plan balances progressive long runs, easy miles and recovery. Start with a realistic base, increase mileage gradually, and test your fueling before race day. Consistency over four months will do more for your finish than any single heroic workout.

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Ethan Brooks

About Ethan Brooks

Ethan Brooks is part of our editorial team and reviews and edits our marathon & half-marathon guides, checking product details against manufacturer specifications and owner feedback.