Training days to race

Pick the race date to see the days and runs left, the long run Sundays, and when to start easing off.

Your details

Until race day

days (12.0 weeks)

Training runs at 3 a week36
Sundays left for a long run12
Taper startsWed 30 December 2026 (2 weeks out)
Weeks and days12 weeks 0 days, or 84 sleeps
Race dayWed 13 January 2027
Long run from 8.0 to 16.0 at 10% a week8 weeks of build, with 10 weeks before the taper
Does it fit?yes, with 2 weeks spare for easier weeks or a cold

Fitness takes about 2 weeks to show after a session, so the last fortnight is for resting, not cramming. Missing a few runs will not undo the work.

Countdown

Weeks, days and sleeps

The result counts down in days, weeks and sleeps, shows the race date, the Sundays left for a long run and when your taper starts. Fitness from a session takes about two weeks to show, so the last fortnight before a half or full marathon is for freshening up rather than catching up.

The working

Twelve weeks out

A race 84 days away is 12 weeks. At 3 runs a week that is 36 runs, with 11 or 12 Sundays for long runs depending on the weekday. A 2 week taper starts 14 days before.

Add your longest run now and the one you want to reach. Building it by 10% a week keeps you well inside the Nielsen 2014 finding that new runners who added more than 30% over 2 weeks had more injuries. From 8 to 16 takes 8 weeks, because 8 × 1.1⁸ = 17.1 and 7 weeks only reach 15.6. With 12 weeks to go and a 2 week taper, there are 10 build weeks, so it fits with 2 to spare for an easier week or a cold. If it does not fit, the page says how far you can get at 10% a week.

Planning the block

Rough shape

Phase	Share of the time
Base: easy running	first third
Build: one quality session a week	middle third
Specific: race pace work	last third, before the taper
Taper	1 to 3 weeks

Missed runs

Life happens

Missing a run or two is fine; do not double up. A week off for illness may mean a slightly gentler goal. Fitness built over months does not vanish in days.

Read with care

What this cannot tell you

ReadinessDays left is not the same as being ready; listen to your body.
InjuryIf you are injured, the race can wait.
IllnessDo not run with a fever or chest symptoms.

Questions

Common questions

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

About 10 to 16 weeks from a regular 5K habit.

When should I start my taper?

1 week before a 10K, 2 for a half, 3 for a marathon.

Is it too late to train?

Even 4 weeks of steady running helps; you may need a gentler goal.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

Before you push on

New to exercise, or got a heart, lung or joint condition? Have a word with your GP or practice nurse first. Stop and get help if you feel chest pain, faintness or unusual breathlessness, and call 999 if it is severe.