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What the 66-day habit study actually says (and why Quitaro uses 60 days)

The famous "66 days" is a median from 39 people forming simple habits, with a range of 18 to 254 days. What it means for quitting, and why Quitaro uses 60.

Quitaro Team

4 min read

In the 2010 study behind the “66 days” figure, the median time for a new daily habit to become automatic was 66 days. But it ranged from 18 to 254 days, and the habits were simple eating, drinking or exercise routines, not quitting nicotine. Quitaro uses 60 days as a commitment window, not a promise.

Quitaro is not a medical device and does not diagnose, treat, cure, or prevent any medical condition.

Where “66 days” comes from

The number comes from a study by Phillippa Lally and colleagues at University College London, published in the European Journal of Social Psychology (Lally et al., 2010).

96 volunteers each chose one eating, drinking or activity behaviour to do daily in the same context, for example “after breakfast”. They kept it up for 12 weeks. Every day they rated how automatic the behaviour felt.

82 participants gave enough data to analyse. The researchers fitted a curve to each person’s automaticity scores. The curve fitted well for 39 of them, and in that group the median time to reach 95% of their plateau was 66 days, with a range from 18 to 254 days.

What the study doesn’t say

  • It isn’t about quitting smoking. The participants were building a new, simple behaviour. Stopping an addictive drug is a different problem, and nicotine withdrawal runs on its own timeline.
  • It doesn’t say habits take 66 days. 66 is the middle of a very wide spread from a small group. The authors stress “considerable variation in how long it takes people”, and that it “can take a very long time”.
  • The longest figures are projections. The study tracked people for 84 days, so estimates beyond that come from extending each person’s fitted curve.

One missed day didn’t undo it

The paper’s most useful finding is easy to overlook: “Missing one opportunity to perform the behaviour did not materially affect the habit formation process” (Lally et al., 2010).

Missing a glass of water isn’t the same as smoking a cigarette mid-quit. But it’s a good reason not to read a slip as proof that you can’t do this.

Why Quitaro uses 60 days

We’ll be straight about it: 60 isn’t a number from this study, or from any study. It’s a design choice, and here’s the reasoning.

  • It covers the hardest stretch. Smokefree.gov, run by the US National Cancer Institute, says the first week after quitting is when you’re most likely to slip. It also says withdrawal symptoms are strongest in “the first few days or weeks” for most people (Smokefree.gov). Sixty days takes you well past both.
  • It’s close to the study’s median, without claiming to be it. Lally’s data suggests that for many people, a daily behaviour starts to feel automatic somewhere around two months. Some are faster and some much slower.
  • It’s a commitment you can hold in your head. Two months is concrete. “Until it feels automatic” isn’t something you can count.

Day 60 isn’t the day the urge disappears. For some people it fades sooner; for others it takes longer. Day 60 is the day you’ve kept a promise to yourself sixty times in a row.

What the 60 days look like in Quitaro

  • Every day you tap Smoke-free today, only if it’s true.
  • A slip restarts the count from day one. That’s the commitment’s rule, not a verdict on your body or your habit.
  • Hold 60 days and you earn the right to gift Quitaro to one invited friend, with no payment.
  • Your one payment is about a month of what you’d spend on cigarettes ($25–$150). Your cigarette money stops burning. It goes into your quit — and 70% of what Quitaro earns goes to the people fighting what you’re quitting, whatever happens with your streak.

See how it works for the daily flow, pricing for the one payment, and Does putting money on the line help you quit? for the research behind the commitment.

What about “21 days”?

That popular figure doesn’t come from this study. In Lally’s data, the fastest anyone reached their plateau was 18 days, and the median was 66. If 21 days passes and quitting still feels like work, nothing has gone wrong.

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