FreeDating.co.uk's survey also indicates the larger a woman is, the more open she may be to having sex on the first date, although there was no similar effect in larger men, but athletic men are most likely to be open to sex on a first date.
Web site officials say they actively discourage people who are looking to cheat on their partner from using FreeDating.co.uk, but they recognize that any dating site will have some married people so they say they ask that they classify themselves as "married."
Although, it's hard to know how many are really married, the survey indicates that men on the Web site who say they are married are most likely to have sex on the first date.
Attributes in women that predict sex on the first date are: medium drinker, interest in cars and spends time in bars, while the attributes in women that don't predict sex on the first date are being a teetotaler and having an interest in bicycling.
Attributes in men that predict sex on the first date are being a medium drinker and smoking, while those not apt to have sex on the first date don't drink, don't smoke and have an interest in cycling.
In women, declining education levels lead to increased willingness to have first-date sex, while in men, the better educated were more willing to have sex on the first date, the survey says.
No further survey details were provided.
Celebrity Families of 2014 [PHOTOS]