Habits · 7 min read

How long does it take to form a habit?

Short answer: about 66 days on average, not 21. In the best-known study, it took people a median of 66 days for a new daily habit to feel automatic, but anywhere from 18 to 254 days depending on the person and the habit. Simple habits tied to a fixed moment form fastest, and missing a single day doesn't reset anything.

66 days

The median time for a daily habit to become automatic (range: 18 to 254 days).

What the research says

In 2010, researchers at University College London followed 96 people for 12 weeks. Each picked one new daily habit, like drinking a bottle of water with lunch, eating fruit, or going for a run before dinner, and did it in the same situation every day. Every day they rated how automatic it felt.

The habits followed a curve: big gains in automaticity early on, then slower progress until they levelled off. On average that took 66 days. Simple habits, like the water with lunch, got there much faster than effortful ones, like 50 sit-ups after morning coffee. And people who missed a day now and then weren't set back in any noticeable way.

Where the “21 days” comes from

In his 1960 book Psycho-Cybernetics, the plastic surgeon Maxwell Maltz noticed that patients needed a minimum of about 21 days to get used to a change, like a new face in the mirror. Retold over decades, “a minimum of about 21 days” became “21 days to form a habit”. It sounds nice, but it was never measured, and it sets people up to give up in week four, just when the curve is still climbing.

How to make a habit form faster

• Tie it to a fixed moment. “After lunch” or “after brushing my teeth”. The same cue every day is what builds the automatic link.
• Start smaller than you think. Five minutes, ten pages, one glass. A habit you do every day beats a big one you skip.
• Grow it slowly. A little more each week, once the start feels easy.
• Never miss twice. One missed day doesn't matter. Two in a row start a new pattern: not doing it.
• Make progress visible. A tick, a streak, a dot that fills up: seeing it is a reward in itself.
• Plan for about two months, not three weeks, so a hard week four doesn't feel like failure.

Example: a 66-day walking habit

A real plan the Dots built from one sentence: “I want to make walking a habit. Make me a 66-day plan starting Monday: a walk after lunch every day, start with 5 minutes and build up slowly.” It starts with 5 minutes, adds a little each week, uses Sundays for a slightly longer walk, keeps one easy rest day a week, and ends at 25 minutes, with a last step to plan what comes next.

Every walk at 13:00, right after lunch, with a reminder.

Frequently asked questions

Is it 21 days or 66 days?

66 days is the average from a study that actually measured it. The 21-day idea goes back to a 1960 book by the surgeon Maxwell Maltz, who wrote that people need a minimum of about 21 days to get used to a change. Over time, “a minimum of” got lost.

Does missing a day reset a habit?

No. In the study, missing a single day did not noticeably slow habit formation down. What matters is getting back to it the next day: never miss twice.

How do I know a habit has formed?

When it feels automatic: you start without deciding to, and skipping it would feel odd. That feeling is what the researchers measured.

Which habits form fastest?

Simple ones tied to a fixed moment, like drinking a glass of water with breakfast. More effortful habits, like a daily workout, took longer in the study.

Sources

• Lally, P., van Jaarsveld, C., Potts, H. & Wardle, J. (2010). How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998–1009.
• Maltz, M. (1960). Psycho-Cybernetics. Prentice-Hall.

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