If you're running London on 24 or 25 April 2027, your 20-week build starts on 5 or 6 December 2026. That's five weeks away.
For the first time, London is a two-day event. The ballot puts you on the Saturday or the Sunday at random, and that one day shifts every date in your plan. Below are the start dates for both, what the 20 weeks should look like, and how to get through a winter build without it taking over your life.
London Marathon 2027 key dates
| Milestone | Saturday runners | Sunday runners |
|---|---|---|
| Race day | Sat 24 April 2027 | Sun 25 April 2027 |
| 20 weeks to go (ideal start) | Sat 5 December 2026 | Sun 6 December 2026 |
| 16 weeks to go (latest sensible start) | Sat 2 January 2027 | Sun 3 January 2027 |
| 12 weeks to go (peak block begins) | Sat 30 January 2027 | Sun 31 January 2027 |
Don't know your day yet? Plan off the Saturday. One extra day of taper never hurt anyone.
Want the session-by-session plan? Download one of our free 20-week marathon training plans – Finish, Sub 4:00, Sub 3:30 or Sub 3:15. For London, week 1 starts on Monday 7 December.
Why 20 weeks (and when 16 is enough)
Twenty weeks gives you room for things to go wrong. And over a UK winter, they will: a cold in January, a week of ice, a work trip.
As a rule:
- First marathon, or under 20 miles a week now: start at 20 weeks. You need the time to build volume safely.
- Running regularly, done a marathon before: 16 weeks works, as long as you can already run for 90 minutes comfortably.
- Chasing a specific time: 20 weeks. The extra month is where the speed work goes.
Starting late isn't the end of the world. Cramming the long runs to catch up is how people end up injured in March.
The four phases of a 20-week London build
Dates below are for Saturday runners; Sunday runners add a day.
- Gauge fitness, weeks 1–4 (5 Dec – 1 Jan). A 30-minute run test in week 1 sets your training zones. Mostly easy running, one long run a week and at least one strength session. Week 4 is a lighter recovery week and lands over Christmas and New Year, so you don't have to pretend the festive period won't happen.
- Faster and stronger, weeks 5–8 (2 Jan – 29 Jan). Quality sessions come in, strength work stays and the long run grows steadily. There's an optional re-test in week 8 to update your zones.
- Volume and race pace, weeks 9–17 (30 Jan – 2 Apr). Your biggest weeks. Long runs with marathon-pace sections, big back-to-back weekends, and practising race-day fuelling on every long run. Weeks 12 and 16 are lighter recovery weeks.
- Taper, weeks 18–20 (3 Apr – race day). Volume drops by around 40–60%, intensity stays. Most people under-taper because resting feels like losing fitness. It isn't.
Long runs are measured in time, not distance. We very rarely set long runs in miles. A 2-hour run is the same training stimulus whether you cover 13 miles or 18, and it stops slower runners spending four hours on their feet chasing a number. In our plans, long runs build gradually and never go over 2 hours 30.
Strength work: one session a week minimum, ideally two. Keep it going right through to the taper. It's one of the best protections against the niggles that derail winter marathon builds.
Training through a UK winter, around a full-time job
Most of the people we coach for London work full-time, and plenty have kids. The plan has to fit the week you actually have.
- Fix your long run day first. Everything else fits around it.
- Run commute where you can. Two runs home a week is free volume.
- Have a dark-and-icy backup. A treadmill or a cross-training session beats a missed day or a fall.
- Expect a bad week. Illness in January is normal. Miss a few days, don't try to make them up, and move on.
This is where a coach earns their fee. When life gets in the way, your plan is rewritten that week in TrainingPeaks rather than you guessing what to cut.
What the two-day format means for you
- Your day is random. Ballot runners are allocated Saturday or Sunday. You can't run both in person.
- Elite races are split by gender. The women's and men's elite and championship fields lead on different days. Organisers haven't yet confirmed which is which.
- Plan travel early. A Saturday race means a Friday expo and travel. Book accommodation and leave as soon as you know your day.
- Your "other" day still counts. Runners can join the virtual MyWay event on their non-race day, which is handy if friends are running the other day.
Source: Marathon Handbook.
London Marathon 2027 FAQs
When should I start training for London Marathon 2027?
Start your 20-week plan on 5 December 2026 for the Saturday race or 6 December for the Sunday race. Experienced runners can start a 16-week plan on 2 or 3 January 2027.
What are the London Marathon 2027 dates?
Saturday 24 and Sunday 25 April 2027. It's the first time London has run over two days.
Can I train for London around a full-time job?
Yes. Most London plans peak at four to six runs a week. A coach builds the plan around your work and family, and adjusts it when weeks go sideways.
How much does a London Marathon coach cost?
1-2-1 marathon coaching with Optimal Endurance costs £85–125 a month, depending on your coach and support level. The first consultation is free.
Do I need to live near London to be coached?
No. Coaching is delivered online across the UK through TrainingPeaks, with in-person sessions available in Harpenden, Hertfordshire and London.
Not ready for 1-2-1 coaching? Start with a free 20-week plan and train alongside our other marathon runners in the OE Club.
Want a coach for London 2027?
We coach first-timers, PB chasers and run-walkers for London and the other spring marathons. Every plan is written for you, not copied and pasted, and adjusted week by week in TrainingPeaks.
1-2-1 marathon coaching starts from £85 a month. If you're near us, see our London and Harpenden coaching pages.
To start on 5 December, get in touch by late November.