The Truth About Habit Formation: Why 21 Days Is A Myth

The notion that it takes 21 days to form a new habit is a myth that has been debunked by sci­ence. In 1960, sur­geon Maxwell Maltz pro­posed that it took 21 days to adopt a new habit based on observ­ing his patients. How­ev­er, recent stud­ies show habit for­ma­tion actu­al­ly takes much longer.

New research from Cal­tech, the Uni­ver­si­ty of Chica­go, and the Uni­ver­si­ty of Penn­syl­va­nia ana­lyzed data from over 30,000 gym-goers and 3,000 hos­pi­tal work­ers to deter­mine how long it takes habits to tru­ly stick. They found that con­trary to pop­u­lar belief, habit for­ma­tion takes months, not days.

Col­in Camer­er, a pro­fes­sor at Cal­tech involved in the study, said “Con­trary to pop­u­lar belief that there is a ‘mag­ic num­ber’ of days it takes to devel­op a habit, we found that it typ­i­cal­ly takes months to acquire the habit of going to the gym, and weeks to devel­op the habit of wash­ing hands in a hos­pi­tal setting.”

The study looked at real-world habit for­ma­tion out­side of con­trolled psy­chol­o­gy exper­i­ments. A 2009 study found it took two months on aver­age to devel­op habits tied to dai­ly cues. How­ev­er, there was sig­nif­i­cant vari­a­tion among the 96 par­tic­i­pants, rang­ing from 18 to 254 days.

While pre­vi­ous research relied on self-report­ed sur­veys, this new study ana­lyzed objec­tive data on gym atten­dance and hand hygiene to deter­mine when habits became auto­mat­ic. The results pro­vide con­vinc­ing evi­dence that 21 days is an unre­al­is­tic time­line for true habit change.

Habit for­ma­tion has major impacts on health, well-being, and pro­duc­tiv­i­ty. Sim­ple habits can reduce men­tal strain, while unhealthy habits can lead to addic­tion and life dis­rup­tion. Gain­ing a bet­ter under­stand­ing of how long habit change tru­ly takes is crit­i­cal to set­ting real­is­tic goals and mak­ing last­ing lifestyle improvements.

The new study con­firms what many peo­ple have expe­ri­enced first­hand — habit change is chal­leng­ing and takes time. There are no short­cuts, but with per­se­ver­ance habits can become sec­ond nature. The 21-day myth should be put to rest once and for all. Real habit change is a marathon, not a sprint.