The 21/66 Day Rule
habits · medium · Depends on the specific habit; minimum 66-day commitment period
What is The 21/66 Day Rule?
Habit formation takes an average of 66 days, not the popular myth of 21 days. Individual variation is substantial (18-254 days) depending on behavior complexity and person.
Is there evidence for it?
EVIDENCEstrong
How do you do The 21/66 Day Rule?
- 1.Choose a new habit and commit to practicing it daily for at least 66 days (not 21)
- 2.Perform the behavior at the same time and in the same context every day
- 3.Track daily completion — expect the habit to feel effortful for the first 3-4 weeks
- 4.Don't expect perfection — Lally's research showed missing a single day does NOT reset progress
- 5.Simple habits (drinking water) automate faster; complex habits (exercise routines) take longer — be patient
How long does it take?
Depends on the specific habit; minimum 66-day commitment period.
Is it hard to start?
medium.
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Source: Phillippa Lally et al. (2010), University College London. Published in European Journal of Social Psychology. 96 participants, 12-week study. The '21-day myth' originated from Maxwell Maltz (Psycho-Cybernetics, 1960).
automaticity · behavior-change · consistency · patience · habit-loop
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