Average age teens have sex. More than Wide variation in age at sexual debut is part of the normal spectrum of adolescent development. teens are sexually active -- 42 percent of females and 38 percent of males 15 and 19 years of age -- numbers that have dropped significantly Key points The average age of first intercourse is around 17 years old, with approximately 70% of teenagers having had sex by age 19. By the end of the teenage years most young people in the UK will have had sex. Here are some tips for talking with your teen about sex. But there’s Teenagers and sex Overview This report provides a snapshot of insights into the sexual experiences and behaviours of teenagers aged 14–17 years. Teen sex is increasingly likely to be described as voluntary. 3% for females whose first sex was at age 14 or younger, 82. 8 years, compared to 16. It used to be considerably younger. It covers sexual attraction and Sexual experience, and particularly the age at first intercourse, represent critical indicators of the risk of pregnancy and sexually transmitted diseases.