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Small rituals, big shifts: what the research says about building habits

It probably takes longer than 21 days, missing a day is fine, and a simple “if–then” plan can make a real difference. Here is what the evidence says.

Mahek Jatana

23 October 2026

2 minutes

The popular claim that a habit takes 21 days to form has very little evidence behind it. Research on how habits actually develop paints a more forgiving and more useful picture: change usually takes longer, but it is also more resilient to the odd bad day than we fear.

It usually takes about two months, and it varies a lot

In a widely cited 2010 study at University College London, Phillippa Lally and colleagues asked 96 volunteers to choose a new eating, drinking or exercise behaviour and repeat it daily. The median time for the behaviour to become automatic was 66 days, but individual times ranged from 18 to 254 days.

A 2024 systematic review and meta-analysis in the journal Healthcare, covering 20 studies and more than 2,600 participants, found a similar pattern. The median time to form a health habit was 59 to 66 days, the average was longer, and individual times ranged from 4 to 335 days.

Missing a day does not reset the clock

One of the most reassuring findings from the UCL study was that missing a single opportunity to perform the behaviour did not materially affect the habit-forming process. Consistency matters over weeks, not perfection on every day.

What makes a habit stick

The 2024 review identified several factors linked with stronger habits:

Frequency. Behaviours repeated more often became habits more reliably.
Timing. Habits practised in the morning tended to be stronger.
Choice. Habits people chose for themselves were stronger than ones assigned to them.
Enjoyment and planning. How people felt about the behaviour, and preparatory routines that made it easier, also mattered.

The power of an “if–then” plan

Psychologist Peter Gollwitzer calls them implementation intentions: plans that link a specific situation to a specific action, such as “If it is 7am and I have made my tea, then I will stretch for five minutes.” In a 2006 meta-analysis of 94 independent tests, Gollwitzer and Paschal Sheeran found that forming implementation intentions had a medium-to-large positive effect on reaching goals.

Putting it into practice

Start smaller than feels necessary: two minutes of reading, five push-ups, one glass of water.
Attach the new habit to something you already do every day, at the same time and place.
Write your if–then plan down.
Expect it to take a couple of months, and treat a missed day as a pause, not a failure.
Choose habits you genuinely want. The research suggests they last longer.