How Long Does It Really Take to Build a Habit? (Hint: Not 21 Days)

Where the 21-day idea came from

The number is usually traced to Maxwell Maltz, a plastic surgeon who wrote the 1960 bestseller Psycho-Cybernetics. He observed that patients seemed to take a minimum of about 21 days to get used to changes such as a new face or a lost limb.

Over time, “a minimum of about 21 days” to adjust turned into “21 days to form a habit”, a much stronger claim that his observation didn’t support.

What the research found

In a study published in 2010, health psychologist Phillippa Lally and her team at University College London followed 96 volunteers who each chose a new daily behaviour, such as drinking a glass of water with lunch or going for a short run before dinner.

On average, it took about 66 days for the behaviour to become automatic, and the range was huge: from 18 days to an estimated 254 days, depending on the person and the habit. Simple habits became automatic faster than more demanding ones.

The most encouraging finding

The same study found that missing a single day did not significantly affect the habit-forming process. Consistency matters over time, but perfection doesn’t.

That means one bad day isn’t failure. The real risk is letting one missed day turn into “I’ve broken my streak, so why bother?” A helpful rule many people use: never miss twice in a row.

How to make new habits stick

• Start tiny. Make the habit so small it feels almost too easy, like one push-up or one page of reading.
• Anchor it. Attach the new habit to something you already do: “After I brush my teeth, I’ll meditate for one minute.”
• Keep the same cue. Doing it at the same time and place helps your brain link the context to the behaviour.
• Make it visible. Put your book on your pillow or your running shoes by the door.
• Track gently. A simple calendar tick is motivating, but treat gaps as information, not judgement.
• Be patient. Plan for a couple of months, not a couple of weeks.

Reframing the journey

If you expect a habit to feel effortless after three weeks, you might give up just as it’s starting to form. If you expect it to take a couple of months, with a few slips along the way, you’re much more likely to keep going. Lasting change is less like flipping a switch and more like wearing a path through grass: every walk makes it a little clearer.