Binge drinking is defined as episodic excessive drinking.[7] There is currently no world wide consensus on how many drinks constitute a "binge", but in the US, the term is often taken to mean consuming five or more standard drinks (male), or four or more drinks (female), on one occasion.[10][11] One definition states that 5 drinks for men and 4 drinks for women must be consumed on one occasion at least once in a two week period for it to be classed as binge drinking.[12] This is colloquially known as the "5/4 definition", and depending on the source the timeframe can vary. In the United Kingdom, binge drinking is defined as drinking more than twice the daily limit, that is, drinking eight units or more for men or six units or more for women (roughly equivalent to five or four American standard drinks, respectively).[13]

Other, less common definitions are based on blood alcohol concentration (BAC). For example, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) recently redefined the term "binge drinking" as any time one reaches a peak BAC of 0.08% or higher as opposed to some (arguably) arbitrary number of drinks in an evening.[14] Whatever the numerical definition used, heavy drinking or rapid consumption over a short period of time with the intention of becoming intoxicated is often implied when the term is used colloquially, since one can remain relatively sober if the four or five drinks are spread out widely over the course of a long evening on a reasonably full stomach.[15]

In the United States, sometimes the term "extreme drinking" or "industrial-strength bingeing" is used to describe a more severe form of (single-evening) binge drinking; it is often defined as ten or more standard American drinks on a single occasion (sometimes as eight drinks for women).[16][17] If done over 2 to 3 hours, a typical adult would have a peak BAC of at least 0.20%.