When to Start Marathon Training
Enter your race date and experience level to find out exactly when to start training — and how many weeks you'll need.
Example Recommendation
Chicago Marathon · October 12 · Intermediate · 20 mi/wk
Leave blank if unsure — we'll use your experience level.
How far in advance should you start marathon training?
The right training window depends on where you're starting from. Here's how many weeks each experience level needs:
| Experience | Training weeks | Notes |
|---|---|---|
| Returning runner | 18 weeks | Needs time to build base safely |
| Intermediate | 16 weeks | Has race experience, solid base |
| Advanced | 14 weeks | High base mileage, structured training |
These are baseline figures. Runners with lower current mileage (under 15 mi/wk) may need an additional 1–2 weeks to build a safe aerobic foundation before formal training begins.
Why your current weekly mileage matters
Your training start date isn't just about how long a plan is — it's about how prepared your body is when training begins. A runner averaging 30 miles per week can step into a 16-week plan right away. A runner averaging 10 miles per week needs to build a base first, or risk injury from ramping too quickly.
Pacerly's marathon training plan generator takes your current mileage into account when building your weekly schedule. If you want to understand how your goal time translates to race-day pacing, the marathon pace calculator can help you set realistic targets before training starts.
What if your race is closer than your ideal training window?
If your race is less than 28 days away, a traditional training plan won't help — focus on easy running and have a solid race-day strategy instead.
If your ideal start date has passed but you still have 8–16 weeks until race day, you're behind schedule but not out of options. A compressed plan can still get you to the finish line safely. The key is honest goal-setting: you may need to adjust your time goal to match your preparation level.
The calculator above will flag both situations and point you toward the right next step.
What to do before training officially starts
If your ideal start date is still weeks away, use that time for base building: easy running 3–5 days per week at a conversational pace. The goal isn't to stress your body — it's to raise your weekly mileage comfortably so you can absorb the structured work of a full training plan when it begins.
A simple pre-training phase might look like 25–30 easy miles per week with one slightly longer run on the weekend. No tempo runs, no track work — just consistent, easy aerobic work that sets you up for the harder training ahead.