English lesbian, gay and bisexual teens first consider their sexuality at 13 years old, but don’t tell anyone else until they are on average two years older.
Four out of five young people tell their friends first and three quarters say that they needed emotional support to come out.
The findings, published today (15 February), are part of an interim report of Metro's Youth Chances project, a five year social study of over 6,000 LGBT youth and their needs.
The study also found that the great majority (80%) of respondents to the Youth Chances survey who identified as lesbian or gay, bisexual or questioning said the first person they told they were gay was a friend.
Nearly three quarters (70%) of respondents to the survey who identified as lesbian or gay, bisexual or questioning said they needed emotional support from someone when they came out.
Commenting on the results, Dan Baker, Metro Youth Chances Project Manager, said: 'These findings reveal some key milestones for young people coming out in the 21st century.
'It is a measure of the progress of LGBT visibility and equality that over half of young people in this generation have come out by the age of 16.
'All the more important is that parents and the wider family, friends, schools, colleges, youth organisations and health services recognise that the majority of young people coming out are saying they need emotional support at this time.'
Metro’s Youth Chances will continue collecting responses right up until 21 March when it will begin in depth analysis of what support is most effective for young people.
Anyone aged 16 to 25 years old can complete the survey (including heterosexual young people) by clicking on this link. Everyone submitting their answers will be entered into a prize draw to win £500.