Atomic Habits vs The Power of Habit: What's the Difference?

Start hereJames Clear writes that readers of Charles Duhigg's book will recognise his terms. Yet one book describes a habit in three steps and the other in four. So how different are they?

Both books describe a habit as a loop that starts with a cue. The Power of Habit (2012) describes three steps: cue, routine and reward. Atomic Habits (2018) splits a habit into four steps and builds four laws on them.

Clear writes that he set out to pick up where Duhigg left off. This page sets the two books side by side, then looks at which of their ideas hold up against the research.

011. At a glance

	The Power of Habit	Atomic Habits
Author	Charles Duhigg, a journalist	James Clear, a writer and speaker focused on habits
First published	28 February 2012, by Random House	16 October 2018, by Avery
The habit loop	Three steps: cue, routine, reward	Four steps: cue, craving, response, reward
How to change a habit	Keep the cue and the reward, and swap in a new routine	Make it obvious, attractive, easy and satisfying
Signature idea	Keystone habits that set off a chain reaction	Identity: each action is a vote for who you want to be
What it covers	Habits of individuals, organisations and societies	Forming good habits and breaking bad ones
How it is written	Research on habits told as stories	Practical strategies, built around four laws
Free to read online	The appendix, a guide to changing habits	Several chapters, posted as excerpts

Our reading: it is the same loop with a different emphasis. Duhigg explains how habits work through stories; Clear gives you a system for building them.

022. What each book argues

The Power of Habit (2012)

Duhigg describes every habit as three steps: a cue that triggers it, a routine (the behaviour), and a reward. A habit, he says, starts as a choice and then becomes a nearly unconscious pattern.

• The Golden Rule. You can never truly get rid of a bad habit, Duhigg argues, so you keep the old cue and the old reward and insert a new routine.

• Keystone habits. Some habits can cause a chain reaction through someone’s life or an organisation. His example for a person is exercise.

• Beyond the person. The book has three parts: the habits of individuals, of successful organisations, and of societies.

Its appendix turns the ideas into four steps: identify the routine, experiment with rewards, isolate the cue, and have a plan.

Atomic Habits (2018)

Clear divides a habit into four steps: cue, craving, response and reward.

• The Four Laws. To build a habit, make it obvious, attractive, easy and satisfying. To break one, turn each law around: make it invisible, unattractive, difficult and unsatisfying.

• Systems over goals. Clear writes that goals “are good for setting a direction, but systems are best for making progress”.

• Identity first. He writes that the key to lasting habits is focusing on creating a new identity first. Each small action, he says, is “a vote for the type of person you wish to become”.

• Small starts. He credits habit stacking, tying a new habit to an old one, to BJ Fogg’s Tiny Habits program. His Two-Minute Rule is to make it easy to start and let the rest follow.

033. Where they agree

• The cue comes first. Both loops start with a cue. A 2016 review of habit research describes people repeating the same behaviours in recurring contexts.

• Make a plan in if-then form. Duhigg describes a habit as a formula the brain follows: “When I see CUE, I will do ROUTINE in order to get a REWARD.” To re-engineer that formula, he writes, the easiest way is to have a plan, “according to study after study.” His own plan read: “At 3:30, every day, I will walk to a friend’s desk and talk for 10 minutes.” He notes that psychologists call these plans implementation intentions. Clear calls habit stacking a special form of an implementation intention.

• The same words. Clear writes that readers of Duhigg’s book will recognise his four stages.

• The same big number. Duhigg’s Q&A credits a paper by a Duke University researcher with finding that more than 40 percent of our daily actions are habits. Clear’s habit guide gives about 40 percent, also citing researchers at Duke.

044. Where they differ

• Three steps or four. Clear makes the craving a step of its own. Duhigg discusses cravings too, but not as a separate step. In his appendix, Duhigg writes that rewards are powerful because they satisfy cravings.

• Swap the routine, or redesign the setup. Our reading: Duhigg’s rule keeps the cue and changes what you do. Clear’s laws work on every step. To break a habit, he says, make the cue invisible.

• How wide they look. Duhigg’s second part covers companies, with chapters on Alcoa, Starbucks and Target. His third part, on the habits of societies, has a chapter on how movements happen, with Saddleback Church and the Montgomery Bus Boycott as examples. Our reading: Clear stays closer to your own daily routines.

055. What holds up in each

The main claims, side by side:

Claim	Where	What the research says
Habits are set off by cues in a familiar setting	Both	Holds up. A 2016 review calls habits “the efficient, default mode of response”.
If-then plans help people follow through	Both	Holds up, but the effect is small. Corrected estimates ranged from d = .35 with one method to d = .15 with a more conservative one.
A habit is a loop that runs on its reward	Both	Partly. Researchers disagree about how much the reward or goal matters once a habit has formed.
About 40 percent of daily actions are habits	Both authors	Partly. Estimates range from about a third to nearly nine in ten, depending on how habit is measured.
Keystone habits set off changes in many others	The Power of Habit	Can’t confirm. We found no study testing keystone habits as a general rule.
Willpower is a muscle that tires with use	The Power of Habit (Starbucks chapter)	Still argued. Large replications found either no clear effect or a small one.
Lasting change starts with identity	Atomic Habits	Can’t confirm. We found no study of Clear’s three layers, and the nearest tests, voting experiments, lean against their original result, though the replications all come from one team.
A new habit takes about 66 days	Clear’s website	Partly. In a 2010 study led by Phillippa Lally, the time ranged from 18 to 254 days; 66 is the median.
Missing one day does not derail a habit	Atomic Habits (ch. 16)	Holds up. In Lally’s study, missing one opportunity to perform the behaviour did not materially affect habit formation.

On the less settled rows:

• The reward. In the model of Wendy Wood and David Neal (2007), goals matter while a habit forms, because they motivate the repetition.

  Once a habit has formed, the setting “triggers the associated response without a mediating goal”.

  Other researchers argue that habits stay goal-driven, and a 2018 study reported five failed attempts to create goal-insensitive habits in people.

• How much of life is habit. In two 2002 studies of US university students, the figures were 35% and 43%. A 2025 study of 105 people in the UK and Australia found 65% of behaviours were habitually set off and 88% habitually carried out.

  In that study, 46% of behaviours were both habitual and in line with what people intended.

• The Golden Rule. We found no study testing the Golden Rule itself on everyday habits, and habit researchers also describe a different route: changing or avoiding the cue.

• Keystone habits. A 2015 review of behavioural spillovers found effects in both directions: one behaviour can lead to another that works the same way, or to one that pushes back against it.

• Willpower. A 23-lab registered replication found an effect whose confidence interval “encompassed zero”. A 36-site study’s preregistered analyses found no evidence for a depletion effect, though an exploratory analysis of its full sample found a small one.

  A preregistered 12-lab study found “a small and significant ego depletion effect”.

• Identity. In 2011, wording survey questions as “being a voter” rather than “voting” raised turnout in two US elections. A larger field experiment in 2016 found no significant difference.

  Two further large replications by the same team, published in 2018 and 2020, also found no effect. The evidence so far leans against the original result, though the replications all come from one team.

• Missing a day. Clear’s rule of thumb, never miss twice, goes one step further; we found no study of “twice” as a threshold.

066. Common mix-ups

Atomic Habits came up with the habit loop. Clear says his picture of the habit loop combines language popularised by Duhigg’s book with a design popularised by Nir Eyal’s book Hooked.

Habits take 21 days. Clear himself traces the 21-day figure to the plastic surgeon Maxwell Maltz. Clear stresses that Maltz was observing, not stating a fact. The studies that measured habit formation found much longer and more varied times.

66 days is the average. Clear’s article calls 66 days an average. A 2024 review reports it as the median, the middle value, in Lally’s study. Across the four studies in that review that measured timing, medians were 59 to 66 days and individuals ranged from 4 to 335 days.

The two books disagree. Our reading: they mostly agree. Clear’s footnote says “Duhigg wrote a great book”, and his four laws are built on the same loop.

077. Which one suits you

Our reading, not a ranking:

• Pick The Power of Habit if you like ideas told through stories, and want to see habits at work in companies and movements as well as in one person.

• Pick Atomic Habits if you want a step-by-step system for your own routines, with a rule for each step.

• Already read one? The core of the other will feel familiar. The free appendix or the free excerpts may be enough.

08Where to go next

• Duhigg’s “A Guide To Changing Habits”: the book’s appendix, free on his website. It walks through the four steps using his own afternoon cookie habit.

• Clear’s chapter 3 excerpt: his four stages and Four Laws, with the footnote about Duhigg.

• Lally and colleagues (2010): the study behind the 66-day figure. 96 volunteers repeated one daily behaviour for 12 weeks.

• Wood and Rünger, “Psychology of habit”: a review of habit research for readers who want the science behind both books.

• Our summaries: Atomic Habits, summarised and The Power of Habit, summarised check each book’s main claims in more detail. Motivation vs discipline covers if-then plans in more depth.

09Quick answers

10Use this

11Quick quiz

How we checked this · Last checked October 2026

• We drew on the authors' own material. For Duhigg, that is the book's appendix and his question-and-answer sheet, both free on his website. For Clear, it is the chapter excerpts and summary he publishes on his website.
• We also read both publishers' pages and the library catalogue record of The Power of Habit.
• For the studies we read the abstracts, plus the full texts of the 2024 habit-timing review, the 2024 if-then meta-analysis and the 2002 and 2025 diary studies.
• Statements that no study exists (of keystone habits or the Golden Rule as general rules, of Clear's three layers) mean none turned up in the Europe PMC and Crossref searches behind our two book summaries.
• Our summaries of each book check the main claims in more detail. This page compares the two.

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