Habit stacking is barely tested, though the idea underneath it holds up better

Key takeaways

• In a 2013 study of 50 people, those told to floss after brushing their teeth, rather than before, had stronger flossing habits and flossed more often eight months later¹.
• That study was small, and its eight-month result came from just 29 people, so it is a promising clue rather than proof².
• A 2025 analysis of 642 tests found that if-then plans, the tested idea underneath habit stacking, help people follow through, especially when they rehearse the plan⁵.
• In an exploratory analysis of programs for people who struggled to take medicines as prescribed, those that linked pills to daily habits showed larger effects than those that didn’t⁸.
• As of April 2026, a Boston Globe report said no large, well-designed studies had shown that habit stacking itself works, and a Wharton expert said there was very little research on it³.

In a study published in 2013, researchers in London ran a simple test with 50 people¹. Everyone got the same encouragement. The only difference was the order.

Half were told to floss before brushing their teeth. The other half were told to floss after¹.

Eight months later, the after-brushing group had stronger flossing habits and flossed more often¹. Tucking the new habit in at the end of an old one seemed to help it stick.

That’s the core of “habit stacking,” the advice to attach a new habit to something you already do every day. “After I pour my coffee, I’ll drink a glass of water.” “After I brush my teeth, I’ll floss.”

The idea fills self-help books and wellness feeds. But the research behind it is thinner than its popularity suggests, and the strongest evidence comes from a related idea with a different name. This guide covers where habit stacking came from, what’s been tested and how to build a stack that holds.

Habit stacking grew out of popular books, not a lab

In April 2026, a Boston Globe report credited BJ Fogg, author of the book Tiny Habits, with creating the approach and James Clear, author of Atomic Habits, with popularizing it³.

Fogg’s method has three parts, according to a Tiny Habits guide hosted on Stanford Medicine’s website⁴. First comes the anchor, a routine already fixed in your day. Next comes a tiny behavior that takes under 30 seconds. Then you celebrate right away with a burst of good feeling⁴.

The method’s recipe reads “After I [anchor], I will [tiny behavior]”⁴. Before starting for real, the guide has you practice the whole sequence back to back, five to eight times⁴.

The guide doesn’t cite studies for its claims about how emotion wires habits into the brain⁴. That doesn’t make the method wrong. It means the details come from practice and experience rather than published trials.

The same report noted that no large, well-designed studies have shown habit stacking works³. Katy Milkman, a Wharton School professor who studies behavior change, was quoted saying there’s very little research on it, though she called the idea intuitive and a good fit with what’s known about habits³.

Researchers have started formal tests. One trial protocol, published in 2020, set out to teach untrained students and office workers in Alabama to do daily bodyweight exercises using Tiny Habits recipes, starting with as little as one push-up¹³.

The tested core is the if-then plan

Habit stacking borrows from a better-studied tool called an implementation intention. That’s a plan in the form “If [situation], then I will [action].”

In 2025, psychologists Paschal Sheeran, Olivia Listrom and Peter Gollwitzer pooled 642 tests of these plans⁵. If-then plans helped people manage their actions, thoughts and feelings, with effects ranging from small to medium⁵. They worked best when people used a true if-then format, cared about the goal and rehearsed the plan⁵. Our article on changing long-held habits covers these plans in more depth.

A habit stack is simply an if-then plan whose “if” is one of your own routines. Gaby Judah, the flossing study’s lead author, recommended in her 2015 doctoral thesis at the London School of Hygiene & Tropical Medicine that such plans name a specific prior action, like arriving home from work².

Even the famous habit-timing study used this trick. In Phillippa Lally’s 2010 study of how long habits take to form, examples of volunteers’ new habits included 50 sit-ups after morning coffee¹².

What the anchoring studies show

We found only a handful of studies that test anchoring directly. Each one is small or limited, so read them as clues.

Flossing. The 2013 study’s results are encouraging, but Judah’s thesis spells out the caveats. At four weeks, the difference between the before and after groups was only a trend that could have been chance. The eight-month result came from just 29 of the 50 people².

Meditation. In 2021, researchers at Arizona State University tested anchors with paying subscribers of the Calm meditation app who hadn’t meditated in the past month⁶. They randomly assigned 167 people to one of three groups: pick your own anchor, use an assigned anchor, or just meditate 10 minutes a day. The final analysis included 101 people⁶.

The assigned anchor was finishing in the bathroom each morning, such as after brushing teeth⁶. That group had modestly higher odds of meditating on a given day, about 14% higher, and their practice faded more slowly during follow-up⁶. People who chose their own anchors did no better than the comparison group⁶.

Every group’s meditating declined over time⁶. About 30% of the anchor-group participants used their anchors often, and nearly all of them had morning anchors⁶. One of the three authors disclosed that she was paid a salary by Calm and owned company stock. The paper states that her pay didn’t depend on the results, but it’s a tie worth knowing about⁶.

Medicines. A 2016 review by Conn and colleagues pooled programs for people who had trouble taking medicines as prescribed⁸. Programs that linked people’s daily habits to taking their medicines had an average effect of 0.57. Programs without that piece averaged 0.22⁸. On common yardsticks, that’s roughly medium versus small⁸.

That finding came from just 12 comparisons, and the authors described this kind of analysis as exploratory⁸. That means it can flag a pattern but can’t show that the habit piece itself caused the bigger effect. Still, it fits the other clues.

Reminders versus routines. Katarzyna Stawarz and colleagues ran a four-week study of habit cues in 2015⁹. Phone reminders helped people repeat a behavior, but they got in the way of the behavior becoming automatic⁹. Cues tied to events in people’s day built more automaticity⁹.

In a separate three-month study that began with 209 people, cues tied to daily events and times of day held up even when routines shifted, such as over holidays¹⁰. Location cues didn’t work well, because routine changes easily disrupted them¹⁰.

Why the order and the details matter

Why would flossing after brushing work better than flossing before? Judah’s thesis points to how the mind chops a day into events. A cue inside the same event, like the moment you finish brushing, may be more reliable than a cue at the boundary between two events².

In plain terms, “while I’m still at the sink” beats “sometime before the bathroom.”

Research also suggests the anchor’s main job is to start the new behavior, not to run it. Some habit scientists split habits into two parts: instigation, the automatic urge to begin, and execution, the steps you go through once you’ve begun¹¹.

In a 2016 study of 229 students, the instigation part of habit predicted how often they flossed, snacked and ate breakfast more consistently than the execution part did¹¹. In a separate study of 123 adults, instigation habit was the only part that uniquely predicted how often they exercised¹⁴.

So a good stack makes starting automatic. Once you’ve started, the rest can still take effort, and that’s fine.

Preparation counts, too. A 2019 editorial by Benjamin Gardner and colleagues pointed to research on exercisers. Having a habit of preparing, like packing a gym bag, predicted how often they exercised over six weeks, while a habit of doing the workout routine itself did not¹⁵. Sometimes the best thing to stack is the setup.

Where stacks break

Most stack failures trace to a few predictable problems. Some are documented; others are informed guesses from habit science.

• A wobbly anchor. If the anchor doesn’t happen every day, in the same way, the new habit has nothing steady to grab. Location cues failed when routines changed¹⁰.
• The wrong spot in the routine. Placing the new behavior at a boundary, before the anchor starts, may be weaker than tucking it in right after¹².
• A new behavior that’s too big. Fogg’s method starts with something under 30 seconds⁴. In Lally’s study, exercise took about 1.5 times as long to become automatic as eating or drinking habits¹².
• Leaning on phone reminders. Reminders can get you to repeat an action without making it automatic⁹. Use reminders to point to the anchor, not to replace it.
• Too many links at once. No study has tested long stacks of several new habits. Habit science suggests one wobbly link can stall the rest, so add one link at a time. This is an informed guess.
• Low motivation. Anchoring may work mainly for people who already want the change, the meditation researchers noted in 2023⁷. In the flossing study, people with more positive attitudes built stronger habits¹.
• A rigid routine that turns into a chore. Very fixed routines may lock in a behavior but become dull, and rigidity may not make you do it more often¹⁵.

One more caution: don’t anchor a new habit to one you’re trying to quit. “After I light a cigarette” keeps the old cue alive. That’s common sense rather than a tested rule.

A stack-builder worksheet

Print this page or copy it into a notebook. It turns the research above into seven steps.

1. List your anchors. Write down 10 things you do every day, from waking up to going to bed. Think small: turning off the alarm, starting the coffee maker, sitting down to lunch, plugging in your phone.
2. Score each anchor. Give one point for each “yes” in the anchor test below. Pick the anchor with the highest score.
3. Shrink the new behavior. Make it small enough to do on your worst day. One push-up, one glass of water, one minute of stretching⁴.
4. Place it right after the anchor ends, in the same spot. “While I’m still at the sink,” not “sometime this morning”¹².
5. Write the recipe and say it aloud. “After I __, I will ____.” Rehearsing the plan made if-then plans work better⁵.
6. Set up the gear. Put the floss by the toothbrush and the mat by the phone charger. Preparation habits predicted how often people exercised¹⁵.
7. Add a second link only when the first feels automatic. For tips on judging that, see our article on how habits form.

The anchor test

Question	Yes = 1 point
Does it happen every single day, weekends included?
Does it happen in the same place each time?
Does it have a clear finish, like turning off a tap?
Would it survive a holiday or a sick day?
Is it something you never skip?

Three sample stacks (hypothetical examples)

Life situation	Anchor	New behavior
Busy parent who wants more water	After I start the coffee maker	I’ll fill a glass of water and drink it while the coffee brews
Retiree who takes a morning pill	After I set my breakfast plate on the table	I’ll take my pill from the box beside the salt shaker (timing approved by my pharmacist)
Desk worker who wants to stretch	After I plug in my phone in the kitchen at night	I’ll do one minute of stretching on the mat that lives there

What the evidence shows

Idea	What studies found	Evidence level
If-then plans, the core of habit stacking	642 tests; small to medium effects, larger with rehearsal5	Strong evidence
Anchoring a new behavior to a routine	One small flossing study; one meditation trial with modest effects16	Promising but early
Linking medicines to daily habits	Larger effects in 12 comparisons; exploratory8	Promising but early
Routine cues instead of phone reminders	Reminders aided repetition but not automaticity in studies by one team910	Promising but early
Doing the new behavior after the anchor, not before	One study of 50, with partial follow-up12	Promising but early
Celebrating right after the behavior	Part of the Tiny Habits method, no studies cited4; one study found rewards ineffective9	Not enough evidence
Long stacks of several new habits	No studies found	Not enough evidence
Habit stacking as a named method	No large, well-designed trials as of 20263	Not enough evidence

Daily rhythms were the original stack

Long before anyone coined “habit stacking,” people tied small acts to daily anchors. A blessing before a meal, a walk after supper and a cup of tea at the same hour each evening all link a practice to something that already happens.

Natural-health traditions often value this kind of rhythm because it works with the shape of a day instead of fighting it. The research gives that instinct some support. Cues built into your own routine outperformed phone reminders in building automatic habits⁹¹⁰.

It also fits a self-reliant streak. When the Stawarz team reviewed 115 habit apps, most focused on tracking and reminders, and few helped people use the events in their own day as cues⁹. Your morning coffee may be a better cue than most apps, and it’s free.

Questions readers ask

The bottom line

Habit stacking is a catchy name for a sound idea: hook a new behavior onto something you already do every day. The if-then planning underneath it has strong support, while stacking itself rests on a few small studies with promising but modest results.

To give a stack its best chance, choose an anchor that never skips a day, make the new behavior tiny, place it right after the anchor ends, rehearse the plan and set up what you need. Add links slowly. If the stack involves a medicine, check the timing with your pharmacist first.

Related reading

• Old habits run on cues rather than willpower, and you can rewire them
• A habit is a shortcut your setting triggers, and this is how one forms
• Behavior science tested its own tricks at scale, and rewards and repetition held up
• Wellness apps help a little if you keep using them, and most people don’t
• What happens when you don’t tell your doctor about supplements

Sources

1. Judah G, Gardner B, Aunger R. “Forming a flossing habit: an exploratory study of the psychological determinants of habit formation.” British Journal of Health Psychology, 2013. researchonline.lshtm.ac.uk
2. Judah G. “An Investigation into the Psychological Determinants of Health Habit Formation.” PhD thesis, London School of Hygiene & Tropical Medicine, 2015. lshtm-eprints-repo-prod.lshtm-eprints.cdl.cosector.com
3. The Boston Globe. “Habit stacking to reach health and wellness goals.” The Boston Globe, April 26, 2026. bostonglobe.com
4. Fogg BJ, Fogg Phillips L; revised by Morioka-Douglas N. “The ASCEND Project: Tiny Habits for Self Compassion: Getting Started.” Stanford Medicine, 2022. med.stanford.edu
5. Sheeran P, Listrom O, Gollwitzer PM. “The when and how of planning: Meta-analysis of the scope and components of implementation intentions in 642 tests.” European Review of Social Psychology, 2025. kops.uni-konstanz.de
6. Stecher C, Sullivan M, Huberty J. “Using Personalized Anchors to Establish Routine Meditation Practice With a Mobile App: Randomized Controlled Trial.” JMIR mHealth and uHealth, 2021. pubmed.ncbi.nlm.nih.gov
7. Stecher C, Cloonan S, Linnemayr S, Huberty J. “Combining Behavioral Economics–Based Incentives With the Anchoring Strategy: Protocol for a Randomized Controlled Trial.” JMIR Research Protocols, 2023. pubmed.ncbi.nlm.nih.gov
8. Conn VS, Ruppar TM, Enriquez M, Cooper P. “Medication Adherence Interventions That Target Subjects with Adherence Problems: Systematic Review and Meta-analysis.” Research in Social & Administrative Pharmacy, 2016. pmc.ncbi.nlm.nih.gov
9. Stawarz K, Cox AL, Blandford A. “Beyond Self-Tracking and Reminders: Designing Smartphone Apps That Support Habit Formation.” Proceedings of CHI 2015, ACM, 2015. discovery.ucl.ac.uk
10. Stawarz K. “Understanding the role of contextual cues in supporting the formation of medication-taking habits.” Frontiers in Public Health conference abstract, 2016. doaj.org
11. Gardner B, Phillips LA, Judah G. “Habitual Instigation and Habitual Execution: Definition, Measurement, and Effects on Behaviour Frequency.” British Journal of Health Psychology, 2016. kclpure.kcl.ac.uk
12. Lally P, van Jaarsveld CHM, Potts HWW, Wardle J. “How are habits formed: Modelling habit formation in the real world.” European Journal of Social Psychology, 2010, as summarized in Jarrett C. “How to form a habit.” BPS Research Digest, 2010. bps.org.uk
13. Hollingsworth JC, et al. “Protocol for Minute Calisthenics: a randomized controlled study of a daily, habit-based, bodyweight resistance training program.” BMC Public Health, 2020. bmcpublichealth.biomedcentral.com
14. Phillips LA, Gardner B. “Habitual exercise instigation (vs. execution) predicts healthy adults’ exercise frequency.” Health Psychology, 2016. dr.lib.iastate.edu
15. Gardner B, et al. “A matter of habit: recognising the multiple roles of habit in health behaviour.” British Journal of Health Psychology, 2019 (accepted manuscript). doi.org