Habits: how long they really take to form, and what helps you build or break one

In everyday speech a habit is something you do often, but in psychology a habit is an action that is triggered automatically by situational cues that have been linked with it in the past. Repeating a simple action in the same situation means that, later, the situation alone sets the action off (Gardner et al., 2012). Because a habit is a process in which a cue creates an impulse to act, that impulse does not always turn into behaviour when it competes with a conscious decision (Gardner, 2015).

An action you first did for a goal, once repeatedly tied to the same place or the same preceding action, comes to be triggered by the situation directly, without going through the goal (Wood & Neal, 2007). That is why habits tend to last even after motivation or interest has faded (Gardner et al., 2012). In two diary studies in which people reported on their day every hour, people doing actions performed almost daily in stable settings were often thinking about something unrelated, and felt less stress (Wood et al., 2002).

Habits run even against what you want. People who habitually ate popcorn at the cinema, largely regardless of hunger or taste, ate as much stale popcorn as fresh, but not when they were somewhere other than a cinema or ate with their non-dominant hand (Neal et al., 2011). This guide uses research to set out how long a habit really takes to form, what helps a new one stick, how to break a bad one, and some common myths.

The idea that a habit takes 21 days is widespread. Habit researchers explain that it appears to have come from anecdotes about patients who had plastic surgery and typically adjusted to their new appearance within 21 days (Gardner et al., 2012). In popular culture it is usually traced to the 1960 book Psycho-Cybernetics (Gardner et al., 2012; Singh et al., 2024).

One study actually measured it: 96 people chose an eating, drinking or activity behaviour to do daily in the same situation, such as “after breakfast”, for 12 weeks, and rated each day how automatic it felt. The 82 with enough data were analysed (the curve fitted for 62, and fitted well for 39), and the time it took for the behaviour to come close to each person’s own peak level of automaticity ranged from 18 to 254 days. As the study lasted 84 days, longer values are estimates from extending the curve (Lally et al., 2010). The often-quoted 66 days is this study’s median (Lally et al., 2010; Singh et al., 2024).

In a systematic review of 20 studies (2,601 people) on forming health-behaviour habits, only 4 reported how long it took: medians of 59 to 66 days and means of 106 to 154 days, with individual times from 4 to 335 days. The authors concluded that most health behaviours take 2 to 5 months to become automatic (Singh et al., 2024). In one of these, a healthy-eating study, the 59-day median was for those who formed a habit, and 23% reached the study’s threshold (Keller et al., 2021; Singh et al., 2024).

It also depends on the behaviour. In a study that used machine learning on the attendance records of 30,110 US gym members and the handwashing records of 3,124 hospital staff, measuring habit as how predictable behaviour became from context, going to the gym typically took 4 to 7 months while handwashing in hospital took a few weeks (9 to 10 shifts). The researchers suggested as one possible reason that gym attendance is a less frequent and more complex behaviour (Buyalskaya et al., 2023). What matters, in the end, is how consistently you repeat something in the same situation rather than the number of days: an action done several times a day would be expected to become a habit in less time than a once-weekly activity (Gardner et al., 2022).

A new habit takes hold when it is repeated with the same cue in the same situation. Choosing a cue within an existing daily routine, such as “when I go on my lunch break”, gives a convenient and stable starting point (Gardner et al., 2012). In a trial that randomised 192 people, linking a behaviour to a routine such as “after breakfast” or to a set time worked similarly, and actually repeating the plan was a key predictor of automaticity (Keller et al., 2021). A small exploratory study (50 people) also found that those told to floss after brushing tended to form stronger habits than those told to floss before, and flossed more often 8 months later (Judah et al., 2013). What is often called “habit stacking” is similar.

If-then plans that set when, where and what you will do also help. In a meta-analysis of 94 studies, people who made such plans reached their goals to a medium-to-large degree more than people who only set goals (d = 0.65; Gollwitzer & Sheeran, 2006; Rozental et al., 2018). A recent analysis of 642 tests found effect sizes of 0.27 to 0.66 depending on the kind of outcome, and larger effects when plans had a proper if-then form, people really wanted to reach the goal, and the plans were rehearsed (Sheeran et al., 2025). These studies did not measure habit formation itself, though. How to make such plans is covered in procrastination: what helps.

Start small and simple. Simpler actions become habits more quickly (Gardner et al., 2012). In a study that followed 111 new gym members for 12 weeks, consistency, a less complex routine, the environment and enjoying the exercise all predicted habit formation (Kaushal & Rhodes, 2015). For the same number of repetitions, habits grew stronger when the behaviour was pleasant or valued for its own sake, whereas thinking it useful or beneficial did not help (an exploratory study of 118 people; Judah et al., 2018).

Keep a record, and make it easy. In a meta-analysis of 138 experiments (19,951 people) that helped people monitor their progress towards a goal, those prompted to monitor reached their goals more than people in control conditions (d = 0.40), and the effect was larger when progress was physically recorded (Harkin et al., 2016). A Cochrane review found that placing food farther away reduced how much people ate (12 studies, 1,098 people), but most studies were in laboratories and the certainty of the evidence was low (Hollands et al., 2019).

Programmes built on habit principles have mostly modest effects. In a meta-analysis of 5 trials (630 people) of habit-based weight-loss programmes, participants lost an average of 1.4 kg more than control groups after 8 to 14 weeks (Cleo et al., 2020), and in a UK primary care trial that randomised 537 people, those given a habit leaflet lost 0.87 kg more than with usual care over 3 months, but after 2 years the usual-care group had lost a similar amount (Beeken et al., 2017). In a study testing 54 four-week programmes with 61,293 members of US gyms, the most effective one offered small rewards for returning after a missed workout (0.40 more weekly visits, 27% more, than a placebo control), but only 8% of the programmes still had a significant effect after they ended (Milkman et al., 2021).

It is easy to think that people with strong willpower are good at resisting temptation. Yet studies including one in which 205 adults recorded their desires for a week found that people with better self-control reported fewer attempts to resist temptation (Hofmann et al., 2012, as cited in Galla & Duckworth, 2015). A meta-analysis of 102 studies (32,648 people) also found that self-control was more strongly linked with automatic behaviours than with behaviours requiring conscious effort (de Ridder et al., 2012).

In six studies (2,274 people), people with more self-control had more settled good habits (in the first study, healthy snacking, exercising and regular sleep), and the researchers concluded that beneficial habits, perhaps more than effortful resistance, may be what links self-control with good outcomes. The studies were not experiments, however, so cause and effect cannot be confirmed (Galla & Duckworth, 2015). The “ego depletion” idea that willpower runs out with use also fared poorly: in a preregistered replication by 23 laboratories with 2,141 people following the same protocol, the effect was small (d = 0.04), with a 95% confidence interval (−0.07 to 0.15) that included zero (Hagger et al., 2016).

Intending is not enough. In a meta-analysis of 47 experiments that changed people’s intentions by a medium-to-large amount, behaviour changed only by a small-to-medium amount (compared with control groups, intention d = 0.66, behaviour d = 0.36; Webb & Sheeran, 2006). Among people who intended to exercise, 46% did not reach the recommended amount (Rhodes & de Bruijn, 2013), and a review notes that interventions that raise knowledge and good intentions typically bring only short-term change (Wood & Neal, 2016). So, for habits, arranging your routine and surroundings so you can repeat something at the same time and place may help more than willpower. Reaching for your phone without thinking is covered in smartphone overuse, and sleep habits in insomnia: what helps.

Breaking a bad habit is different from forming a new one and takes more effort (Gardner et al., 2012). Habits build up slowly and do not shift much with current goals or occasional exceptions (Wood & Neal, 2007). They do falter when the situation that triggers them changes: the exercising, newspaper reading and TV watching habits of students who transferred to a new university survived only when the setting stayed the same, and when it changed, students sometimes acted on their current intentions instead (Wood et al., 2005).

So the period right after a big change such as moving house may be a good time to start new habits. In a field experiment with 800 participants, an intervention promoting a sustainable lifestyle worked better among people who had recently moved, and the “window of opportunity” seemed to last about 3 months after the move (Verplanken & Roy, 2016). Searches for “diet”, gym visits and goal commitments also rise after moments that feel like a fresh start, such as a new week, month or year, or a birthday (Dai et al., 2014).

Plan what you will do instead, rather than what you will not do. Plans that only say what not to do, such as “I will not eat crisps”, actually strengthened the habit, especially when it was strong (Adriaanse et al., 2011a). Plans that named another action for the same situation could override the habit, but behaviour changed only when people really wanted that alternative (Adriaanse et al., 2011b). In a Swedish study that followed 1,066 people with New Year’s resolutions for a year, 55% of those who responded at one year said they had kept their resolution, and resolutions framed as doing something were kept more often than those framed as not doing something (58.9% vs 47.1%; Oscarsson et al., 2020).

For habits already set in stone, diary studies found that the most helpful approach was vigilant monitoring, noticing the moment and telling yourself not to do it. It did not weaken the habit itself, though, and in these studies avoiding the cue did not help with strong habits (Quinn et al., 2010). One review concludes that a two-pronged approach, breaking unhealthy habits while building healthy ones at the same time, is best for lasting change (Wood & Neal, 2016).

For repetitive behaviours that are hard to stop on your own, such as nail biting, thumb sucking or tics, there is a behavioural therapy, delivered with a therapist, called habit reversal training (HRT). In a meta-analysis of 18 studies (575 people), it had a large effect compared with control conditions (d = 0.80; Bate et al., 2011). The individual studies were small, though. Tics are covered separately in tics and Tourette syndrome.

For trichotillomania, repeatedly pulling out one’s hair, a meta-analysis of 24 medication and behavioural therapy trials (857 people) found that behavioural therapy including habit reversal training also had a large benefit compared with control conditions (Farhat et al., 2020). For repeated skin picking there were only 2 randomised trials of habit reversal training, and the methods of the trials reviewed were of questionable quality (Lee et al., 2019). If such behaviours go on to the point of getting in the way of daily life, they may be conditions that need diagnosis and treatment, so talk to a professional.

If you keep going despite knowing it harms you, spend more and more time on it, and feel distressed or strongly pulled when you stop, it may be an addiction or a compulsion rather than a simple habit. In that case, see the guides on gaming disorder, gambling, smartphone overuse, alcohol use, drug addiction and OCD. The gaming guide also explains why gaming every day out of habit is not a disorder on its own.

Myth 1: A habit takes 21 days. The figure appears to come from anecdotes about how plastic-surgery patients adjusted (Gardner et al., 2012), and in a study that actually measured it, times varied widely, from 18 to 254 days (Lally et al., 2010). Contrary to the belief in a “magic number” of days, going to the gym took months and handwashing in hospital took weeks (Buyalskaya et al., 2023).

Myth 2: Miss one day and you have to start again. Missing one opportunity did not materially affect habit formation (Lally et al., 2010). Studies have found that the impact of a missed day was temporary and faded over time (Gardner et al., 2022). Just as rewarding people for coming back after a missed workout worked best, what matters is picking it up again the next day (Milkman et al., 2021).

Myth 3: You need strong willpower to form habits. People with more self-control tended to rely on good habits rather than gritting their teeth against temptation (Galla & Duckworth, 2015). That does not mean willpower plays no part: people who kept their New Year’s resolutions reported using more stimulus control, rewards and willpower than those who did not (Norcross & Vangarelli, 1988).

Myth 4: Enough motivation is all you need. Even large changes in intention changed behaviour less (Webb & Sheeran, 2006), and 46% of people who intended to exercise did not do as much as recommended (Rhodes & de Bruijn, 2013). Habits, by contrast, tend to last even after motivation or interest fades (Gardner et al., 2012).

Myth 5: Giving up after a few days means your will is weak. We found no study of quitting after exactly three days, but one study followed 200 people with New Year’s resolutions for 2 years. 77% kept their pledge for the first week but only 19% for 2 years, and even among those who succeeded, 53% slipped at least once, with an average of 14 slips over the 2 years (Norcross & Vangarelli, 1988). Slipping is common, and moments that make people want to start again, like a new week or month, keep coming (Dai et al., 2014).

Q. How can I tell whether something has become a habit? A. If you find yourself doing it whenever the situation comes up, without having to think or make an effort, it is a sign it has become a habit (Gardner et al., 2012). Most research, too, measures this by asking people to rate it themselves (Gardner, 2015).

Q. Can I build several habits at once? A. We found no study that compared this directly. Since simpler actions become habits faster (Gardner et al., 2012), starting with one small habit is our suggestion.

Q. Do habit apps or habit trackers work? A. No particular app was tested in the studies here. But in experiments that prompted people to monitor their progress, they reached their goals more than people in control conditions, especially when they wrote it down (Harkin et al., 2016).

Q. Is it better to do it in the morning? A. In a small study of 48 students, those who stretched in the morning were estimated, by extending their curves, to reach automaticity sooner than those who stretched in the evening (Fournier et al., 2017), but this is not a rule. A systematic review also found morning habits generally stronger, though it was based on few studies (Singh et al., 2024).

Q. Can the Big Five test tell me whether I will form habits easily? A. No. The Big Five personality test looks at five personality traits, including conscientiousness, which is linked with steadiness; it does not predict whether habits will form easily.

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