How long does it take actually to form a new habit?

People often say it takes 21 days to form a habit. Others claim it’s more like 66 or 70 days. But in my personal experience, there isn’t a magic number. It’s less about the total number of days and more about how frequently and consistently you repeat the behavior.

All habits follow a similar trajectory: they move from effortful practice to automatic behavior. This process is called automaticity — the ability to perform an action without consciously thinking about each step. It happens when the nonconscious mind gradually takes over, freeing up mental energy for other tasks.

In other words, habits don’t form because the calendar says 21 days have passed. They form when your brain builds strong enough associations through repetition. For some, that might take a few weeks; for others, several months. What matters most is consistency over time, not the number itself.

Reference: Atomic Habits by James Clear

 In the beginning (point A), a habit requires a good deal of effort and concentration to perform. After a few repetitions (point B), it gets easier, but still requires some conscious attention. With enough practice (point C), the habit becomes more automatic than conscious. Beyond this threshold—the habit line—the behavior can be done more or less without thinking. A new habit has been formed.