Two might be company and three a crowd, but it seems four is perfect when it comes to friends.
The average woman needs this number at any one time in her life, a study suggests.
Researchers say females are becoming far more selective and will bother forming close bonds only with those they know they can trust and share experiences.
Having four friends is also ideal as it makes up a group of five - which ensures no one is ever left out, the researchers say.
If two or three women begin confiding in each other or sharing a joke there is always another person for the others to talk to.
A study of 1,000 women aged 18 to 45 found that just under half (49 per cent) believe that four is the perfect number of best friends to have.
By contrast just one in five thought having three close friendships was best.
This finding contradicts the famous scenario in the Sex and the City TV series and films in which Sarah Jessica Parker's character Carrie Bradshaw is content to have three close friends - Charlotte, Miranda and Samantha.
A better example might be the five protagonists of the TV series Desperate Housewives, although Teri Hatcher's character Susan Mayer's fellow housewives Bree, Edie, Lynette and Gabrielle may not always act in the most loyal, friendly way.
The poll, commissioned by the Silver Bay Point wine range, found that only one in 25 thought it preferable to have more than 50 close friendships.
The study also found that within each group there are usually clearly defined roles such as the agony aunt, the homemaker, the career girl, the socialite and the quiet one.
Females responding to the survey said that the most important factors determining friendships were being able to share confidences and experiences.
