The study of more than 4000 women seeking birth control found that 45 percent overestimated the effectiveness of the pill and condoms, reported Reuters.
According to Scope, subjects of the study were asked to rate different birth control options.
According to scientists, women whose partners use condoms experience a 2 percent per-year pregnancy rate with perfect use and a 15 percent per-year pregnancy rate with typical use.
With the pill there is about a 0.3 percent chance of unintended pregnancy if used perfectly.
The most effective birth control methods are intrauterine devices (IUDs) and contraceptive implants, which release hormones slowly to prevent pregnancy.
"We need to do a better job of educating the public -- women and men -- on the failure rates with typical use," said study author David L. Eisenberg, of Washington University in St. Louis School of Medicine, reported Reuters.
The research was published in the journal American Journal of Obstetrics and Gynecology.