Our Methodology

How we turn medical data into accurate percentiles

15,521
Total Measurements
20
Studies Analyzed
17
Countries Represented
2015
Meta-Analysis Year

Our Primary Data Source

Our calculator is based primarily on the most comprehensive meta-analysis of penis size ever conducted, supplemented with additional studies for validation.

Veale et al. (2015) Meta-Analysis

Published in BJU International, this systematic review and meta-analysis combined data from 20 studies with standardized measurement protocols. It remains the gold standard for penis size statistics.

15,521
Men Measured
17,000+
Data Points
5.16"
Mean Length
4.59"
Mean Girth

Why This Meta-Analysis?

Studies Included in Our Dataset

These are the primary studies that contributed to our calculator's database:

Study Year Sample Size Country Population
Wessells et al. 1996 80 USA Adult men
Schneider et al. 2001 111 Germany Young adults (18-19)
Promodu et al. 2007 301 India Adult men
Herbenick et al. 2014 1,661 USA Sexually active men
Acuña et al. 2010 800 Colombia Military recruits
Khan et al. 2012 609 Pakistan Adult patients
Habous et al. 2015 778 Saudi Arabia Adult men
Aslan et al. 2011 2,276 Turkey Military personnel
Chrouser et al. 2013 5,122 Tanzania Adult men
Söylemez et al. 2012 1,132 Turkey Healthy volunteers

Note: This represents a selection of the most significant studies. The complete meta-analysis includes additional smaller studies that meet our inclusion criteria.

How Medical Measurements Are Taken

Consistency in measurement is crucial. All studies in our dataset follow these standardized protocols:

📏
Length Measurement
Measured from pubic bone to tip (bone-pressed), using rigid ruler, with penis perpendicular to body. Room temperature controlled.
⭕
Girth Measurement
Circumference at midshaft or widest point, using measuring tape. Consistent location across subjects within each study.
🏥
Professional Measurement
All measurements by medical professionals or trained researchers. No self-reported data included in our calculations.
🌡️
Standardized Conditions
Controlled room temperature, privacy ensured, consistent time of day when possible, same position for all subjects.
💊
Erection Method
Pharmacologically-induced (injection) or self-stimulated in private. Maximum erection verified before measurement.
📊
Multiple Measurements
Many studies take 3 measurements and use the average, reducing measurement error and increasing accuracy.

What We Don't Include

Studies We Exclude and Why

Why Self-Reported Data Is Problematic

Studies consistently show that self-reported measurements average 0.5-1.5 inches larger than medical measurements. This is due to:

How We Calculate Your Percentile

We use statistical modeling based on the normal distribution observed in the data:

The Statistical Method

Penis size follows a normal (Gaussian) distribution. Using the mean and standard deviation from our dataset, we calculate your exact percentile position.

Z-score = (Your Size - Mean) / Standard Deviation
Percentile = Normal CDF(Z-score) × 100

Our Statistical Parameters

Length
Mean: 13.12 cm (5.16 in)
SD: 1.66 cm (0.65 in)
Girth
Mean: 11.66 cm (4.59 in)
SD: 1.10 cm (0.43 in)

This means 95% of men fall between 4.0-6.3 inches in length and 3.7-5.4 inches in girth. If you're in this range, you're completely normal.

Our Commitment to Transparency

What We Promise

Limitations to Consider

While our data is the best available, it has limitations:

Why We Don't Separate by Race/Ethnicity

The scientific evidence shows minimal statistically significant differences between ethnic groups when studies use proper methodology. The variations within groups are much larger than between groups. We use global data to avoid perpetuating stereotypes not supported by medical evidence.

Primary References

Our main sources for those who want to verify:

Ready to See Your Real Percentile?

Now you know exactly where our data comes from. No tricks, no agenda, just medical science.

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