Average Penis Length in Adult Males
The average erect penis length in adult males is approximately 13.1-13.6 cm (5.1-5.4 inches), based on the most rigorous systematic review of clinician-measured data.
Evidence-Based Measurements
Erect Length
- The most comprehensive systematic review analyzing 692 men found a mean erect length of 13.12 cm (SD 1.66 cm) when measured by healthcare professionals using standardized procedures 1.
- A large U.S. study of 1,661 sexually active men reported a mean erect length of 14.15 cm (SD 2.66 cm), though this relied on self-measurement which tends to overestimate 2.
- A focused review of 10 studies with clinician measurements (n=1,629) found a combined mean of 13.61 cm (5.36 inches), which is more reliable than self-reported data 3.
Flaccid and Stretched Length
- Mean flaccid pendulous length: 9.16 cm (SD 1.57 cm) based on 10,704 men 1.
- Mean stretched length: 13.24 cm (SD 1.89 cm) from 14,160 men, which closely approximates erect length 1.
- Stretched length measurements are clinically useful as they correlate strongly with erect dimensions 1.
Circumference Measurements
- Mean erect circumference: 11.66 cm (SD 1.10 cm) from 381 men 1.
- Mean flaccid circumference: 9.31 cm (SD 0.90 cm) from 9,407 men 1.
- A U.S. study reported mean erect circumference of 12.23 cm (SD 2.23 cm) 2.
Clinical Context and Common Pitfalls
Self-Reported vs. Clinician-Measured Data
- Self-reported measurements consistently overestimate penis size by approximately 0.5-1.0 cm due to volunteer bias and social desirability bias 3.
- Studies relying on self-measurement often report means around 15.75 cm (6.2 inches), which do not reflect actual population averages 3.
- Men seeking penile lengthening surgery typically overestimate what constitutes "normal" size, with 85% believing normal length should be 10-17 cm 4.
Population Variations
- Ethnic and geographic variations exist but are relatively modest (1-2 cm differences between populations) 5, 1.
- An Indian study found mean erect length of 13.01 cm and circumference of 11.46 cm, demonstrating some population-specific differences 5.
- The strongest correlation with penis size is height (r = 0.2 to 0.6), though this explains only a small portion of variance 1.
Clinical Implications
- In a study of 67 men seeking penile lengthening, none had measurements below the 2.5th percentile for normal range 4.
- Most men seeking surgery have normal-sized penises and would benefit from counseling with normative data rather than surgical intervention 3, 4.
- The American Urological Association considers penile lengthening surgeries risky and generally not indicated for men with normal dimensions 3.