It takes anywhere from a few weeks to several months to form a habit, depending on the person, the behaviour and the context. The popular claim that it takes 21 days is a myth. A 2010 University College London study by Phillippa Lally and colleagues found wide variation and no fixed number, with simple habits forming faster than complex ones.
Where the 21-day idea comes from
The "21 days" figure is usually traced to a 1960 book by plastic surgeon Maxwell Maltz, who noticed that patients seemed to take around 21 days to adjust to their new appearance. He wrote that it takes "a minimum of about 21 days" for old mental images to dissolve. Over decades that careful remark turned into a rule: "any habit takes 21 days".
It was never a study of habit formation. It was an observation about adjusting to a change, and "minimum" got lost along the way. If you have ever quit a habit on day 22 feeling like a failure, you were holding yourself to a number that was never established.
What the research actually found
The study most often cited was published in the European Journal of Social Psychology in 2010 by Phillippa Lally, Cornelia van Jaarsveld, Henry Potts and Jane Wardle. Volunteers chose a new eating, drinking or activity behaviour and reported each day how automatic it felt.
The main findings, in plain terms:
- The time to reach automatic behaviour varied widely between people and between behaviours.
- It took many weeks on average, far longer than three weeks for most.
- Simpler behaviours became automatic faster than complicated ones.
- Missing one opportunity did not seriously damage the process.
Treat this as one well-known study with a particular group of volunteers, not as a law of nature. The practical lesson is the point: there is no finish line at day 21, and forgiving yourself for a missed day is part of the process.
What changes how long a habit takes
| Factor | Faster | Slower |
|---|---|---|
| Complexity | One small action | Several steps, special equipment |
| Context | Same time and place every day | Different each day |
| Cue | Tied to an existing routine | "Whenever I feel like it" |
| Reward | Immediate and noticeable | Distant or invisible |
| Start size | Tiny version first | Full-size from day one |
| Motivation | Personally meaningful | Doing it because you "should" |
| Stress and sleep | Reasonable | Chronic overload |
Notice that most of these are design choices, not character traits. If a habit is taking a long time, the question is rarely "what is wrong with me?" and more often "what can I change about the setup?" The design steps are in how to build habits.
The stages you will probably go through
The following is a practical way of thinking about it, not a measured timetable. Your pace will differ.
Stage 1: Effortful (first weeks)
Every repetition takes a decision. You forget, you negotiate, you do the small version. This is normal. The job is simply to show up, in the smallest form, as often as you can.
Stage 2: Wobbly (the middle)
The novelty wears off. Life gets in the way: a trip, an illness, a busy week. This is where many people quit, because the habit feels neither new nor automatic. Plan for this stage by deciding in advance what your minimum version is and what you will do after a missed day: do the small version the next day, no catching up.
Stage 3: Easier (getting automatic)
You start doing it without a fight. You may notice that you feel slightly off when you skip it. Cues now trigger the behaviour most of the time. This is the point to consider adding a second habit, or increasing the size of the first one a little.
Stage 4: Maintenance
The habit mostly runs itself, but it is not permanent. Big disruptions such as moving house, a new job or travel can break the cues. Expect to rebuild parts of it after a change, and be prepared to re-use the same method.
How to tell whether a habit is forming
Instead of counting days, ask:
- Do I remember it without a reminder?
- Does starting take less effort than it did two weeks ago?
- Can I do the small version even when I am tired?
- Do I feel something missing when I skip it?
If you can answer yes to most of these, the habit is well on its way. A simple tool like the habit tracker lets you look at the pattern of ticks over weeks, which is more informative than a single streak number.
Do streaks help or hurt?
Streaks can be motivating: they make your consistency visible. They can also backfire. If a single miss resets a counter to zero, the "what the heck" effect kicks in and people drop the habit altogether. Better rules:
- Count "days done this week" instead of "days in a row".
- Never miss twice in a row.
- Keep a minimum version that counts as done.
Speeding things up without forcing it
You cannot force a habit to form on a schedule, but you can remove drag:
- Make the action smaller until it is nearly effortless.
- Use the same cue every time, for example by stacking it onto an existing routine.
- Prepare your environment the night before.
- Reward right after, with a tick, a note or a moment of noticing.
- Review weekly and fix the biggest obstacle.
Habits and personal growth
For habits connected to doing more things on your own or getting out of your comfort zone, the timeline can feel even less linear, because each outing is a new situation. Many people find it helps to record how they felt before and after. Solo Era is an iPhone app that lets you rate how nervous you felt before and after each mission and plots progress over time, with a photo journal for your notes. It does not promise a particular timeline; it simply makes small steps visible so you can see your own pattern.
Solo Era for iPhone
Try it with Solo Era
Solo Era gives you one realistic mission a week, records how nervous you felt before and after, and keeps a photo journal of what you did. An iPhone app. A subscription is required to start missions; any free trial depends on the offer and eligibility shown in the app.
If you are stuck on a habit that never seems to become automatic, why you cannot stick to habits walks through the usual causes.
Keep reading
- 30-Day Habit Challenge: A 30-day habit challenge to build one small habit: pick it, shrink it, attach it to a cue and track it with a four-week plan that survives bad days.
FAQ
Is it really 21 days to form a habit?
No. The 21-day idea comes from an observation in a 1960 book, not from habit research. The best-known study on habit formation found wide variation, with many people needing much longer than three weeks.
Is it 66 days then?
You may see 66 days quoted as an average from the 2010 UCL study. It is better to treat it as an example of how long it can take rather than a target, because individuals ranged from much shorter to much longer.
What if I miss a day?
Return to the habit the next day. In the research, missing a single opportunity did not significantly affect habit formation. What matters is not missing twice in a row, and not letting guilt stop you restarting.
Why do some habits form faster than others?
Simple, specific behaviours in a stable context with immediate rewards form faster. Complex habits with several steps, changing contexts or delayed rewards take longer.
Can I speed up habit formation?
You can reduce friction: shrink the action, choose a reliable cue, prepare the environment and reward yourself. You cannot skip the repetitions, but you can make each one easier.
Solo Era for iPhone
Try it with Solo Era
Solo Era gives you one realistic mission a week, records how nervous you felt before and after, and keeps a photo journal of what you did. An iPhone app. A subscription is required to start missions; any free trial depends on the offer and eligibility shown in the app.
