How long does it take to form a habit?

By No Rush · Updated October 23, 2026

The short answer

There is no fixed number of days. In a study by Phillippa Lally and colleagues, it took between 18 and 254 days before a new daily action felt automatic. Doing it at the same moment each day helped. A skipped day set it back only a little, so the next day you simply do it again.

Is the 21-day rule true?

No single number of days works for everyone, so 21 days is not a rule. In a study by Phillippa Lally and colleagues, 96 people picked something to eat, drink or do at the same moment each day, like after breakfast. The time until it felt automatic ranged from 18 to 254 days.

The study ran for 84 days. The longer times are estimates drawn from each person's curve, so nobody in it was followed for 254 days. For most people the action got easier fastest at the start, and after that the curve levelled off.

How do you start a new habit?

Attach one small action to something you already do every day, in the same place. Wendy Wood and colleagues had people keep diaries and found that about 43 percent of what they did in a day was repeated in the same setting, mostly without thinking. A new habit borrows that moment, like right after you switch on the kettle.

A big change in your life can be a good moment too. In a study by Verplanken and Roy with about 800 people, a campaign for greener habits worked better for those who had moved house in the three months before.

What happens if you skip a day?

In Lally's study, skipping one day changed little about how the habit grew. A later guide by Benjamin Gardner, Amanda Rebar and Phillippa Lally puts it this way: after a skipped day the habit slips back a little, and it builds up again once you carry on. The day after a gap is just the next repetition.

Do reminders help you build a habit?

A reminder on your phone helps you remember, and you end up doing it more often. In their research on habit apps, Katarzyna Stawarz, Anna Cox and Ann Blandford found that reminders can also hold back the point where it starts to happen by itself. You lean on the alarm instead of on the moment in your day.

In the No Rush app

In the app, you set up one small habit under Your rhythm. You pick the habit, and then the moment in your day when you do it: a time, or right after something you already do every day. The app counts how often you did it this month. After four weeks it asks if the habit is helping you. If it is not, you remove it and choose a new one.

No Rush app

An iPhone app for people who feel stuck. It sets out one small next step at a time and tells you why that one. It is not therapy.

Sign up free Take the test For iPhone. Coming soon to the App Store. The first seven days are free in the app. After that, you choose whether to subscribe. Sign up now and the app stays free for you, for life.

Sources

Lally, van Jaarsveld, Potts & Wardle (2010). How are habits formed: modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998-1009. doi.org/10.1002/ejsp.674
Gardner, Rebar & Lally (2022). How does habit form? Guidelines for tracking real-world habit formation. Cogent Psychology, 9(1), 2041277. doi.org/10.1080/23311908.2022.2041277
Wood, Quinn & Kashy (2002). Habits in everyday life: Thought, emotion, and action. Journal of Personality and Social Psychology, 83(6), 1281-1297. doi.org/10.1037/0022-3514.83.6.1281
Verplanken & Roy (2016). Empowering interventions to promote sustainable lifestyles: Testing the habit discontinuity hypothesis in a field experiment. Journal of Environmental Psychology, 45, 127-134. doi.org/10.1016/j.jenvp.2015.11.008
Stawarz, Cox & Blandford (2015). Beyond self-tracking and reminders: Designing smartphone apps that support habit formation. Proceedings of the 33rd Annual ACM Conference on Human Factors in Computing Systems, 2653-2662. doi.org/10.1145/2702123.2702230