The popular 21-day figure doesn’t hold up. Research suggests it often takes around two months, and the range is wide.
Key ideas
- In a widely cited 2010 study, it took a median of 66 days for a new daily behavior to feel automatic.
- The time varied widely between people, from 18 to an estimated 254 days.
- Missing a single day didn’t materially set people back.
- Repeating a simple action in the same situation is the core of forming a habit.
You’ve probably heard that it takes 21 days to form a habit. It’s a tidy number, but the research tells a different story.
What the research found
In a study published in the European Journal of Social Psychology in 2010, researchers at University College London asked 96 volunteers to choose a new daily behavior, such as eating a piece of fruit with lunch or running before dinner, and to do it in the same situation every day for 12 weeks. Each day, participants rated how automatic the behavior felt.
| Finding | What it means |
|---|---|
| Median of 66 days to reach automaticity | About two months, not three weeks |
| Range of 18 to an estimated 254 days | It varies a lot between people and habits |
| Missing one day made little difference | Consistency matters, but perfection doesn’t |
How habits work
A habit is an action your brain links to a particular situation, or cue. When you repeat the same action after the same cue, such as stretching right after you get out of bed, the link gets stronger until the action starts to happen with less thought.
That’s why the situation matters as much as the action. “Exercise more” is a goal. “Walk for 10 minutes after lunch” is something you can repeat until it becomes a habit.
Making a new habit easier
- Start small. Two push-ups or one glass of water is easier to repeat than an ambitious routine. You can build up later.
- Tie it to a cue. Do the new habit straight after something you already do every day. Our guide to habit stacking shows how.
- Keep the situation the same. The same time and place make the link stronger.
- Remove friction. Lay out your walking shoes or keep a water bottle on your desk.
- Track it. A simple checklist on paper or in an app helps you see your progress.
Small step
Expect the first few weeks to take effort. If a habit still feels like work after a month, that’s normal and doesn’t mean you’re failing.
When you slip
Busy weeks, illness and travel will break your streak at some point. The research suggests one missed day doesn’t undo your progress, so get back to it at the next opportunity rather than waiting for a fresh start on Monday.
A note on health
If you want to change a habit that affects your health, such as smoking or drinking alcohol, your doctor can tell you about support that improves your chances of success. For help to quit smoking, the free quitline 1-800-QUIT-NOW is available across the US.
A realistic timeline
Plan on giving a new habit at least two months of steady practice. Pick one change at a time, such as a morning routine, and add the next once the first feels automatic.
Still wondering?
Where does the 21-day idea come from?
It has been repeated in self-help books for decades, but research on habit formation suggests most habits take longer than three weeks.
Are some habits harder to form than others?
Yes. In the 2010 study, more demanding behaviors, such as an exercise routine, tended to take longer to become automatic than simple ones, such as drinking a glass of water.
What should I do if I miss a day?
Pick up again at the next opportunity. The study found that missing one chance to do the behavior didn’t materially affect the habit-forming process.
This article is general information about everyday health habits, not medical advice. If you have a health condition, are pregnant or take regular medication, talk to your doctor or another qualified health professional before making big changes to your diet, activity or sleep. Figures come from US public health sources such as the CDC, HHS and the Dietary Guidelines for Americans.