It 's an age-old worry for the men the world over . Now , however , scientists have revealed what 's considered 'normal ' for penis size and length . The average length of an erect penis is 5.2 inches ( 13.12 cm ) , they found . Meanwhile , the average length of a flaccid penis is 3.6 inches ( 9.16 cm ) and 5.2 inches ( 13.24 cm ) when flaccid but stretched . And when it comes to girth , the average erect circumference was 4.6 inches ( 11.66 cm ) and 3.7 inches ( 9.31 cm ) when flaccid . The British research also found there was a small correlation between the erect length of a penis and a man 's height . The average length of a flaccid penis is 3.6 inches ( 9.16 cm ) and 5.2 inches ( 13.24 cm ) when flaccid but stretched , the researchers found ( file photo ) The researchers say the graphs they have plotted , which show the size distributions of a penis , will help clinicians dealing with Body Dysmorphic Disorder ( BDD ) , a serious anxiety disorder relating to body image . The study could help to counsel men worried about their size , or with investigations into how condom failure relates to penis size and girth . Some men are concerned about their penis size , and those who are preoccupied and severely distressed may even be diagnosed with BDD . The researchers created a graph ( or a nomogram ) depicting the size distributions of penis ' among men of all ages and many races . The research included 17 studies of 15,521 men who underwent penis size measurements by health professionals using a standard procedure . Before this research , there had been no formal systematic reviews of these measurements , and no attempt to create a nomogram showing the distribution of size . Lead author Dr David Veale from the Institute of Psychiatry , Psychology & Neuroscience ( IoPPN ) , King 's College London and South London and Maudsley NHS Foundation Trust , told MailOnline : 'Men compare themselves in locker rooms and with pornography on the internet and believe they are inferior . 'Some men have been teased by sexual partners about their length . 'There are lots of men who might be worried - and we think reassuring men they are in the normal range will help . 'We will also use the graphs to examine the discrepancy between what a man believes to be their position on the graph and their actual position , or what they think they should be . 'We have a specialist Body Dysmophic Clinic and some men are very worried and distressed about their size . Experts plotted graphs showing the size distribution of the length of the average penis when flaccid , flaccid and stretched and erect . The graph above shows average penis length of men - in centimetres - in each percentile . The researchers also plotted a nomogram showing the size distribution of the girth of the average penis . The graph shows the average penis girth of men in each percentile - again in centimetres . 'They are unlikely to be helped just by looking at a size distribution graph , they will need more formal treatment like Cognitive Behaviourhal Therapy or medication too . ' Dr Martin Baggaley , medical director at South London and Maudsley NHS Foundation Trust , said : 'BDD causes a person to have a distorted view of how they look and they can spend an obsessive amount of time worrying about their appearance . 'This can include worries over their weight , specific parts of their body and , for men , the size of their penis . 'This can take over someone 's life and cause a great deal of distress . 'Hopefully this new study will help reassure those many men who are concerned with their penis size and assist clinicians dealing with BDD . ' 'BDD occurs alongside Obsessive Compulsive Disorder ( OCD ) and a person with BDD may constantly compare their looks to other people 's , spend a long time in front of the mirror or avoid the mirror altogether , constantly conceal a perceived defect or feel anxious when around other people or in social situations . ' The research was published in the British Journal of Urology ( BJU ) .
Experts have detailed graphs showing the size distributions of a penis . The average flaccid penis is 3.6 inches ( 9.16 cm ) , the research shows . This extends to 5 inches ( 13.24 cm ) when stretched but still flaccid . Researchers found a small correlation between height and penis size . Graphs could help in treating Body Dysmorphic Disorder , say experts .