Research shows the average penis size has grown by 25% over the past three decades, but it’s still probably smaller than you think. The average penis size is not nearly as big as many people think it is! A 2020 review of research on penis size found that the average length of an erect penis is between 5.1 inches and 5.5... So, our analysis of penis size data comprises 142 countries based on multiple data source and was mainly oriented by Veale et al. (2014) and Lynn's (2013) comprehensive scientific studies. When comparing these datasets, measurement methods vary considerably between studies. Find out what you need to know about the average penis size and discover the factors that influence it.