What is the average flaccid vs erect penis size and how do they correlate?

1. What the best measurements say about average size

Large meta-analyses and systematic reviews that relied on investigator-measured data report mean values that converge: multiple sources give an average flaccid length near 9.16–9.22 cm and an average erect length in the 13.1–13.8 cm range, with one pooled analysis reporting erect mean 13.84 cm from 5,669 men and flaccid mean 9.22 cm from 28,201 men ^{[2] [1] [7]}. Other large pooled reviews report similar erect means (~13.12 cm) and stretched lengths around 12.8–13.2 cm, reinforcing that most measured cohorts place erect length in the roughly 13–14 cm band ^{[1] [8] [2]}.

2. Stretched length, girth and the anatomical picture

“Stretched” length—when a flaccid penis is gently extended—tends to approximate erect length and is commonly used clinically because it’s easier to obtain in non-erect settings; pooled stretched-length estimates are around 12.8–13.2 cm, which overlaps measured erect means ^{[2] [8]}. Girth averages reported alongside length place flaccid circumference near 9.3 cm and erect circumference near 11.66–12.0 cm in the larger reviews, giving a fuller anthropometric picture beyond length alone ^{[1] [3] [9]}.

3. Correlations: what predicts what

Multiple studies find that flaccid length is a weak predictor of erect length—smaller flaccid penises often lengthen proportionally more (“growers”), while larger flaccid penises sometimes lengthen less (“showers”)—so visual flaccid appearance correlates poorly with erect outcome ^{[5] [10]}. Stretched length shows the strongest and most consistent correlation with erect length and is therefore used as a practical proxy in clinical nomograms ^[4]. Somatic correlations exist but are modest: height shows the most consistent relationship with stretched/erect length with reported correlation coefficients roughly r = 0.2 to 0.6 in pooled analyses ^[4].

4. Variability, percentiles and what “average” conceals

Studies illustrate wide individual variation: flaccid lengths in the literature range from ~5.2 cm to ~13.8 cm across studies, and erect measurements span a comparable range, meaning averages mask broad spread and percentile differences in any population ^{[11] [9]}. One review notes an erect penis of about 10 cm falls near the 5th percentile, while lengths substantially above 16–17 cm sit in higher percentiles — the clinical nomograms published with these reviews are intended to contextualize individual measurements ^{[1] [7]}.

5. Measurement methods, biases and limits of the evidence

Reliable estimates come from investigator-measured cohorts; self-reported data inflate means and increase variance, and volunteer bias (men with larger penises being more likely to participate) can skew samples, so methodological choices matter when comparing studies ^{[2] [6]}. Temporal and geographic heterogeneity also appears in the literature—some meta-analyses examine trends over decades and note possible increases, but differences in sampling, measurement technique, and study design limit causal interpretation ^{[11] [12]}.

6. Bottom line and clinical context

The consensus from measured, peer-reviewed data is that average flaccid length sits around 9–9.5 cm and average erect length around 13–14 cm, with stretched length serving as the best single clinic-ready predictor of erect length and modest positive correlation with height; nonetheless, flaccid appearance alone cannot reliably indicate erect size because of large individual variability ^{[1] [2] [4]}. Where precision matters—medical counseling, surgery evaluation or research—clinicians rely on standardized measurements and published nomograms rather than impressions or self-report ^{[7] [4]}.