How long does it take to break a bad habit?

Research suggests there's no single answer. The popular "21 days" claim is a myth stemming from a misread of plastic surgeon Maxwell Maltz's 1960s observations. A more rigorous 2010 study by Phillippa Lally at University College London found that habit formation takes anywhere from 18 to 254 days, with an average of about 66 days before a behavior becomes automatic. The timeline depends on the complexity of the habit, how deeply ingrained it is, your consistency in replacing it, and individual differences in neurology and motivation. Simple habits break faster than complex ones tied to emotional triggers or addiction. The key factor isn't time itself but consistent repetition of a replacement behavior until it becomes the new default.