Habits: how long it really takes for them to stick

In psychology, a habit is more than something you do often. It is an action that a particular situation triggers automatically, like putting on your seatbelt after getting into the car. Once an action is linked to its cue in this way, it needs little attention or motivation.²

Where the 21 days come from

You often hear that a new habit takes 21 days. That figure appears to go back to anecdotal observations of patients after cosmetic surgery, who typically got used to their new appearance within about 21 days.² It has little to do with building new behaviours.

What the study shows

In the best-known study on the subject, 96 volunteers chose a new eating, drinking or activity behaviour and a fixed moment for it, such as “after breakfast”. For twelve weeks they did it every day in the same situation and rated each day how automatic it felt. Automaticity rose quickly at first, then more and more slowly, until it reached a personal plateau.¹ The median time to reach 95% of that plateau was 66 days.²

The differences were large: among participants whose progress could be modelled, it took anywhere from 18 to 254 days. Values beyond 84 days are projections, because the study lasted only twelve weeks. Missing a single day did not materially set anyone back.¹

What newer data say

A 2024 review pooled 20 studies with 2,601 participants, covering physical activity, healthy eating and flossing among others. In the four studies that measured the time it took, the median was 59 to 66 days and the mean 106 to 154 days, with a range of 4 to 335 days. Morning habits and habits people chose themselves tended to become stronger.³

Starting small pays off

Simple actions become habits faster than complicated ones. A journal for family doctors therefore advises starting with a small step, such as walking one or two stops before getting on the bus rather than the whole way. Every small success can also build confidence for the next change.²

In that sense, habits work much like a savings plan: the effort comes at the start, and after that it runs almost by itself. Our article on the minimum dose of strength training shows which small steps do a lot for your health.