According to sex experts the best sex lasts for between seven and thirteen minutes and even a three minute quickie can be satisfying.

A major survey by Canadian and American sex therapists has concluded that the ideal length of time to have penetrative sex is under fifteen minutes.

The research was prompted by the confusion in the public domain about how long intercourse should last, an issue which sometimes causes distress to both men and women even though it is often for quite different reasons.

In order to quantify the problem the expert sex therapists came up with what was "adequate," "desirable," "too short," and "too long" intercourse.

The research revealed that the average sex therapist believes an "adequate" length for intercourse was from 3 to 7 minutes; "desirable" from 7 to 13 minutes; "too short" from 1 to 2 minutes and "too long" from 10 to 30 minutes.

The study is the first to review what the experts believe is the ideal length of time to have intercourse.

Lead researcher Dr. Eric Corty, from the Behrend College in Erie, Pennsylvania, says research has shown that the expectation by many people is that sex should last much longer and this expectation he says leads to disappointment and dissatisfaction.

Dr. Corty says the research should help eliminate unrealistic beliefs that healthy sex should last a long time.

Dr. Corty says the fantasy model of male sexuality harboured by both men and women, has men with large penises, rock-hard erections, who can sustain sexual activity all night long.

He says the study provides a realistic model of sexuality, which is useful both in treating people with sexual concerns and dysfunctions, and on a broader level will help prevent the onset of sexual dysfunctions.

Australian experts say there is a dearth of data on Australians' expectation of sex but anecdotal evidence suggests most Australian women would be happy with the therapists' "adequate" time of three to seven minutes, while men would not.

The study concludes that intercourse which lasts from 3 to 13 minutes is normal and says the dissemination of this information to the public may change what are often unrealistic expectations which cause distress.