The Measured Numbers
Most pages answering this question quote figures from marketing material. These come from published studies, so you can weigh them against whatever a clinic tells you.
The largest comparison followed 301 men treated between 2017 and 2021:
| Material | Peak gain | Reached at | Change by 24 weeks |
|---|
| PMMA (permanent) | 2.9 cm | 4 weeks | Minimal decline |
| Hyaluronic acid | 2.6 cm | 4 weeks | Down 19.2% |
| Poly-lactic acid | 2.1 cm | 12 weeks | Down 14.3% |
A separate ultrasound-guided case using 5 mL of cross-linked hyaluronic acid recorded a smaller change — midshaft circumference from 12.3 cm to 13.0 cm, a gain of 0.7 cm.
So the honest range is somewhere under a centimetre to around three centimetres of circumference, depending on material, volume and your starting anatomy. In inches, that is roughly a quarter-inch to just over an inch of girth.
Read the timing carefully
Notice that peak gain is measured at 4 weeks — while swelling is still resolving and product has not fully settled. The 24-week figures are the ones that describe what you keep.
A clinic quoting peak numbers without mentioning the decline is quoting the most flattering moment in the data.
Why Your Result May Differ
- Starting anatomy. The same volume produces a different proportional change on different tissue.
- Volume placed. More product means more girth — but forcing too much into one session produces contour irregularity rather than a better outcome, which is why larger increases are staged.
- Tissue plane. Placement between the dartos and Buck's fascia distributes evenly. Superficial placement risks visible nodules.
- Your metabolism. Hyaluronic acid is broken down at different rates by different people.
Length Is a Different Question
No injectable meaningfully increases length. Filler adds circumference. Any provider claiming otherwise is misrepresenting the procedure — see girth vs length for what the surgical options involve and why the AUA considers suspensory ligament division unproven.
What "2 Inches" Claims Mean
If you have seen advertising promising two inches, compare it against the table above. The best-performing material in the largest published series produced 2.9 cm — a little over an inch — of circumference, not length.
Claims substantially beyond that are either measuring at peak swelling, describing surgery, or simply untrue. We wrote a separate piece on why those claims are a red flag.
Setting a Realistic Goal
The SMSNA notes that most men seeking enhancement have anatomy within normal range, and that self-assessment correlates poorly with measurement. Before choosing a target, it is worth reading what average actually is.
At consultation, Dr. Daniel Moghadam will measure, tell you what volume is safe for your tissue, and give you a realistic figure rather than the one you hoped to hear.
