honest answer · peer-reviewed · no age-range gimmicks
Does Size Change With Age?
Short answer: not really. Adult size is essentially stable from late teens through your 60s. We could have made 10 different pages for each age bracket — but that would be misleading.
The TL;DR
Adult penis size is largely fixed from ages 18-21 onward.
The global average of 13.12 cm erect (Veale et al. 2015, n=15,521) applies across all adult age groups. Significant age-related changes only appear in later decades (70+) and are typically subtle.
At what age does growth stop?
Penis growth is driven by testosterone and typically completes during puberty. Most measurement studies find final adult size is reached between ages 16 and 18, with some late-developers continuing small changes up to age 21. After that, size stabilizes.
Why there is no 18-24 vs. 25-34 vs. 35+ breakdown here
Many sites publish separate "average size by age range" pages with different numbers for each bracket. These numbers are almost always drawn from small subgroups of larger surveys, and the differences between them are statistical noise — not real biological variation.
The peer-reviewed meta-analyses that pool data across adult ages find no meaningful difference between a 22-year-old, a 35-year-old, and a 55-year-old. Your percentile at 25 is the same as your percentile at 45.
What actually changes with age
Size is stable. These things are not:
- Erectile firmness — gradually decreases, with a noticeable shift often around ages 40-50.
- Speed of arousal — slower response to stimulation becomes more common from the 40s onward.
- Refractory period — time between erections lengthens significantly from the 30s.
- Morning erections — frequency decreases with age and can be an early marker of cardiovascular or hormonal changes.
- Perceived fullness — many men report a perception of "shrinkage" after 60 that is often more about erection firmness than actual size change.
Does size actually decrease in later life?
After roughly age 70, small decreases in length (often 0.5-1 cm) and girth can occur due to vascular changes, reduced testosterone, decreased smooth-muscle tone, and changes in connective tissue. These changes are subtle, individual, and usually smaller than people expect.
Significant or rapid changes at any age warrant a conversation with a urologist — not a comparison chart.
So what should you do with this?
If you are looking up "average size by age," what you actually want is a percentile calculator — that gives you a real answer regardless of your age. The percentile at 18 is the percentile at 48.
Skip the age gimmick
Use the percentile calculator. It works at any age and gives you an actual number.
calculate your percentile →Disclaimer: Educational / entertainment content. Not medical advice. If you are concerned about changes in size or erectile function, consult a urologist.