The amount of time it takes to form a habit depends on the: person context activity environment frequency of repetition complexity of the habit trigger's strength habit's stability reward strength motivation
In the 1950s when Dr. Maltz, a plastic surgeon, observed his patients took about 21 days to get used to their new faces with changes like a nose job. Some experienced phantom limbs after amputation for about 21 days. This single-clinic observation was marketed by self-help authors and turned into the commonly accepted myth – it takes 21 days to make or break a habit.
In an exercise program designed to prevent patients or elders from falling, participants acquired the program’s teaching as a habit in approximately 7 weeks.
A study asking participants to adopt a new eating, drinking, or activity behavior suggests it takes an average of 66 days to form a habit. Researchers estimated it would take 18 to 254 days for the new behavior to become automatic.
146 participants aged 18-61 years chose a specific new habit to build from 60 including financial, health, environmental, and personal habits (habits like saving money, exercising, recycling, self-care, etc.). Monitoring habits increased habit strength, and so did more repetition by the 3rd month.
The belief about what it takes to start a habit and commitment to a habit can impact the time needed to form the habit. It can take just a few repetitions or weeks.
Summary: A few repetitions can be enough. But it might take 3+ months. Your beliefs about forming the habit affect how well you form it.