How Long Does It Really Take to Form a Habit?

You've probably heard it takes 21 days to build a habit. The research tells a more honest story.

The 66-day finding

In a 2010 study, Phillippa Lally and colleagues at University College London followed people adopting a new daily behavior. On average it took 66 days for the behavior to feel automatic — but the range ran from 18 to 254 days depending on the person and the habit.

Importantly, missing a single day did not meaningfully derail the process. Consistency over time mattered more than perfection.

What this means for your streak

Streaks are useful because they make consistency visible. But a broken streak isn't a broken habit. If you miss a day, the most useful move is simply to show up the next day.