It Takes 21 Days to Build a Habit

Picture week four of a leadership program. A participant admits that her new habit, a two-minute check-in with one team member every morning, still feels like work. "I thought this was supposed to be automatic by now." Many of us have heard that a habit takes 21 days. A study from London puts the typical figure at 66, which makes her right on track.

The 21 days are neat, and they come with a nice story. In 1960, plastic surgeon Maxwell Maltz wrote that his patients needed about three weeks to get used to their new face. Over the years, the three weeks became a rule for habits of every kind.

Psychologist Phillippa Lally and her colleagues at University College London put the idea to a test. They asked 96 volunteers to build a daily habit, such as a piece of fruit with lunch or a 15-minute run before dinner, and to rate each day how automatic it felt. Among the participants whose data allowed a clear estimate, the typical (median) time was 66 days. The fastest got there in 18 days; for the slowest, the researchers' model projected 254, well beyond the study's 12 weeks. And the good news: missing a day now and then made little difference.¹

¹ Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W., & Wardle, J. (2010). How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998–1009. https://doi.org/10.1002/ejsp.674