What is the global average erect penis length by age group?
Executive summary
Available research and health reporting converge on an average adult erect penis length of roughly 5.1–5.5 inches (about 13.1 cm). Sources that break size down by age say most penis growth happens in puberty, with adult size generally reached by late adolescence (around 18–21), though reported ranges for teens and study methods vary [1] [2] [3].
1. What the major reviews say: a clear adult average
Systematic reviews and widely cited overviews put the mean erect adult length in the 5.1–5.5 inch range; for example, a 2015 review measured by health professionals produced an average erect length of about 13.12 cm (5.17 in), and mainstream health outlets cite a probable average of 5.1–5.5 inches [4] [3] [1].
2. How age figures into growth: puberty is decisive
Penis length increases primarily during puberty; sources state the majority of growth occurs between about ages 13–16 and that penis size typically reaches its adult range by late adolescence—around 18–21—after which length is generally stable into adulthood [2] [1].
3. Reported ranges for teenagers: wide and method-dependent
Health guides and educational sites offer ranges rather than precise averages for teens. One site reports that by late adolescence the average erect length falls between 5.1 and 5.7 inches, while another places typical 16‑year‑old erect length between about 4.7 and 6.3 inches—illustrating substantial spread and dependence on sampling and measurement methods [2] [5].
4. Why published numbers differ: measurement and sampling matter
Discrepancies across studies arise from who measured (health professionals vs. self-report), how they measured (base-to-tip pressed to the pubic bone vs. softer techniques), and volunteer bias in self-measured samples. Reviews measured by professionals tend to report lengths around 5.1–5.3 inches; self-report studies often show more divergence, sometimes inflating averages [4] [6].
5. Age-specific averages: what the sources do and don’t provide
Sources consistently describe the growth curve (little change before puberty, rapid growth during adolescence, stability in adulthood) but do not offer a single, globally accepted table of average erect length by narrow age bands (e.g., year-by-year from 12–25) in the materials provided. Some outlets give approximate ranges for “late adolescence” or specific ages like 16, but a uniform, global age-by-age average is not presented in these sources [2] [5] [3].
6. Small declines later in life and body‑composition effects
Reporting notes that erectile function and apparent penis size can change with aging, health, and body composition—greater pelvic fat can make the penis appear smaller (buried penis), and vascular or hormonal changes can affect erections—yet sources say length is largely stable after adolescence unless health changes occur [3] [2].
7. What’s reliable and what’s not: methodological transparency matters
The most reliable estimates come from systematic reviews and measurements by clinicians; self-reported studies are prone to volunteer and reporting bias and can overstate mean lengths. Readers should prefer professional measurement studies when seeking an authoritative number [4] [6].
8. Practical takeaway for parents, teens and clinicians
Clinically and in public reporting, an erect adult penis averaging about 5.1–5.5 inches is the working number. Pubertal growth usually finishes by late adolescence; wide individual variation is normal; and concerns about development should be discussed with a healthcare provider because available sources emphasize clinical assessment for outliers or worries [3] [1].
Limitations and sources of disagreement: the reviewed materials agree on the general adult average and the puberty growth window but disagree in exact ranges cited for teens and differ by study method. Available sources do not provide a single, authoritative global table of erect penis length broken down year-by-year by age group [2] [5] [4].