How Many Days Does It Take to Form a Habit? (Hint: It’s Not 21 Days)

If you've ever tried forming a new habit—like starting a morning workout, drinking more water, or learning a new skill—you’ve probably asked: "How many days does it take to form a habit?"

The internet is full of answers: 21 days, 30 days, even 90. But the truth is, there's no fixed number—because habit formation depends on what you’re doing, how often you do it, and who you are.

In this guide, we’ll break down what science really says about habit-building timelines, what influences speed and success, and what you can do to create habits that actually stick.

What the Science Really Says: The 66-Day Rule Explained

The idea that it takes 21 days to form a habit comes from a misinterpretation of older studies. However, a more reliable answer came in 2009, when Dr. Phillippa Lally and her team at University College London conducted one of the most cited studies on habit formation.

The study, published in the European Journal of Social Psychology, tracked 96 people over 12 weeks as they formed new habits like drinking water after breakfast or doing sit-ups after coffee. The results?

Average time to form a habit: 66 days

Range: 18 to 254 days

Simpler habits like drinking water took 18 days

More difficult habits like daily sit-ups took over 80 days

Dr. Lally noted that habits form based on consistent repetition in a stable context. The more complex the behavior, the longer it takes.

Why Some Habits Take Longer Than Others

Let’s explore the factors that influence how fast a habit forms:

1. Habit Complexity

The more complex a habit is—like building an exercise routine or meditating for 20 minutes daily—the more mental effort it takes. Simpler habits (like taking a vitamin or writing a one-line journal entry) form faster.

2. Consistency and Environment

Habits thrive in stable environments. Doing a behavior at the same time, in the same place, and under the same conditions helps your brain recognize the pattern faster.

• Use tools like a habit calendar or habit tracker app to reinforce routine.

• Design habit-friendly situations: remove distractions, set reminders, and simplify your space.

3. Identity-Based Habits

Rather than focusing on outcome-based goals like "I want to lose 10 pounds," focus on identity-based habits like "I’m the type of person who exercises daily."

BJ Fogg (Stanford Behavior Lab) says: “Tiny habits that reinforce identity create long-term momentum.”

What Happens When You Miss a Day?

A common fear is that missing a day will "break" your habit. Fortunately, that’s not true.

“Missing once is a mistake. Missing twice is the start of a new habit.” — James Clear, Atomic Habits.

The key is how quickly you bounce back:

• Evaluate setbacks: What caused you to miss?

• Adjust goals: Was it too ambitious?

• Refocus: Remove friction and return to the behavior quickly

How Many Days Does It Take to Form a Habit?

How to Make Habit-Building Easier: The Flow State Strategy

One way to speed up habit formation is by entering what psychologists call the flow state—a mental state where you’re fully immersed and performing at your best. Flow happens when a task is challenging enough to push you without overwhelming you. Research suggests the sweet spot is about 4% harder than your current ability.

Dr. Ann Graybiel (MIT) explains: “The basal ganglia helps turn repeated, rewarding behaviors into automatic routines.”

Why This Matters:

• Too easy = boredom

• Too hard = frustration

• Just right = engagement and habit memory

This is the idea behind 4% Challenge Rule—where you push yourself just slightly beyond your comfort zone to stay in flow, stay motivated, and build consistency.

What Other Experts Say

Not all scientists agree on the 66-day average.

• Dr. Benjamin Gardner (King’s College London): Habit strength depends more on automaticity than on days.

• BJ Fogg advocates for starting with tiny habits and scaling naturally.

• Some behavior models favor statistical modeling tools to predict habit formation based on effort and consistency.

It’s not just about time—it’s about method, mindset, and measurement.

Why Habits Fail (And What to Do About It)

Here are the three biggest mistakes I made (and what you can avoid):

Mistake #1: Starting Too Big 

Most people try to go from zero to hero overnight. Want to get fit? They plan 90-minute gym sessions. Want to eat better? They overhaul their entire diet. This overwhelms your brain and guarantees failure.

The Solution: Make It EASY

 Start so small it feels almost silly. Your brain needs to learn the pattern before it can handle the intensity.

• Instead of: "I'll work out for an hour"

• Try: "I'll do 2 push-ups after I brush my teeth"

• Why it works: Any habit should take less than 2 minutes to start. You're establishing the pattern, not achieving your end goal immediately.

Mistake #2: No Clear Trigger 

You have good intentions, but you rely on remembering to do your habit. Your brain is already managing thousands of decisions daily—it doesn't have bandwidth for "remembering" new behaviors.

The Solution: Make It OBVIOUS.

Create environmental cues that make your habit impossible to ignore.

• Instead of: "I'll meditate sometime today"

• Try: "I'll meditate for 2 minutes right after I pour my morning coffee"

• Why it works: If you have to think about whether to do your habit, it's not obvious enough. Make the trigger so clear that NOT doing it feels weird.

Mistake #3: No Immediate Reward 

Most habits have long-term benefits (health, wealth, relationships) but no immediate payoff. Your brain craves instant gratification, so it defaults to easier, more immediately rewarding behaviors.

The Solution: Make It FUN/REWARDING.

Build immediate positive reinforcement into every habit.

• Instead of: Forcing yourself through boring workouts

• Try: Only watching your favorite show while on the treadmill (habit bundling)

• Why it works: The moment you complete a habit, celebrate it (even with just a fist pump). This creates a positive association that makes you want to repeat the behavior.

Read More: Temptation Bundling

Make Habits Stick with Gamification

Most people fail to build habits because they get bored or distracted. That’s why I built the Moore Momentum App—a gamified habit tracker that:

• Uses variable rewards to keep things interesting

• Tracks your small wins

• Helps you progress across your Five Cores of life: Mindset, Career and Finances, Relationships, Physical and Emotional Health 

Conclusion: So, How Long Does It Take to Form a Habit

Forming a habit isn’t about following a fixed rule.

It’s about:

• Choosing the right behavior

• Making it easy and repeatable

• Tracking your progress

• Staying engaged by making it “just hard enough”

With consistency, the right tools, and an identity-based mindset, anyone can create habits that last a lifetime.