Odds are you’ve been told it takes 21 days to form a new habit. Or, maybe you’ve been told it takes 30 days. Or, maybe 45. Or, maybe 66. Or, in all likelihood, you’ve heard many random numbers over the years. Well, I’m going to give you the definitive answer for the length of time it takes to form a new habit once and for all.

The Origin Of The Myth: It Takes 21 Days To Form A New Habit

In the 1950s, Dr. Maxwell Maltz was a plastic surgeon with a penchant for psychology. Dr. Maltz observed that it would take his patients who received a nose job about 21 days to become accustomed to their new face. Similarly, Dr. Maltz observed that his patients would experience phantom limb pain for about 21 days when an arm or leg was amputated. Naturally, Dr. Maltz began to reflect upon the length of time he spent adjusting to change and new behaviors himself, and he noticed it would take him about 21 days too.

So, in 1960, reflecting upon his experience with his patients, Dr. Maxwell Maltz published Psycho-Cybernetics, a self-help book based on improving the concept of self through techniques such as establishing a positive outcome through visualization of that positive outcome. In the book, Dr. Maltz shares the observations he made of his patients and wrote, “These, and many other commonly observed phenomena tend to show that it requires a minimum of about 21 days for an old mental image to dissolve and a new one to jell.” The book was a hit and would go on to sell more than 30 million copies as well as influence the core techniques of many personal development experts such as Zig Ziglar and Tony Robbins.

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In the years that followed, as word spread of Dr. Maltz’s views, two subtle distortions emerged. First, Dr. Maltz’s perceptions were mistaken for scientific fact when in fact they were just his observations. And second, his words were curtailed to mean something entirely different. Instead of requiring “a minimum of about 21 days” as Dr. Maltz had originally put forth, it became easier and more definitive to simply say, “It takes 21 days to form a new habit.” 21 days sounds long enough to be believable, but short enough to be achievable. Plus, if you’re selling an idea, you want to sound authoritative and not leave any doubt over “minor” technicalities.

Is There Scientific Evidence On How Long It Takes To Create A New Habit?

Dr. Maltz did not conduct a scientific case study to arrive at his conclusion of taking about 21 days to form a new habit. He was simply making casual observations about his patients and himself.

However, decades after the release of Dr. Maltz’s best-selling book, health psychology researcher Phillippa Lally and others at University College London did conduct a scientific study to measure the length of time it takes to form a new habit. Originally published in 2009, the study found it took an average of 66 days to form a new habit. But, and this is important, the 66 days reported in the study was an average. Of the 82 participants who provided sufficient data for analysis, it took anywhere from 18 days to 254 days to form a new habit. In other words, as the study concludes, there is “considerable variation in how long it takes people to reach their limit of automaticity [or forming a new habit]” and “it can take a very long time.”

The Definitive Answer For The Length Of Time It Takes To Form A New Habit

The reality is there is no definitive answer, and the length of time it takes to form a new habit is different for everyone. You may find you’re able to create a new habit in as little as one month. But, it’s far more likely that forming a new habit will be harder than what you’ve been led to believe and could take quite some time.

If you’re motivated to create a new healthy habit, specify clearly what you intend to do and in what situation you intend to do it. For example, I plan to leave the house 20 minutes after I wake up and use the treadmill at the gym for 30 minutes on Mondays, Tuesdays, Thursdays, and Fridays. Then, be consistent in your action. The key to forming new habits is to persevere.

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