To measure your penis accurately, you need a rigid ruler for length and a flexible measuring tape (or a piece of string) for girth. Measurements should be taken while fully erect for the most consistent results. The whole process takes about two minutes once you know where to place the ruler and tape.
How to Measure Length
Place a rigid ruler or straight measuring tape along the top of your penis, starting where the shaft meets your abdomen. Press the end of the ruler firmly against the pubic bone. This is important because the fat pad above the base can hide a significant portion of length, and pressing into it gives you what’s known as the “bone-pressed” measurement. This is the method used in clinical studies, so it’s the one you want if you’re comparing to published averages.
Measure in a straight line from the pubic bone to the very tip of the head. If your penis has a noticeable curve, a flexible measuring tape laid along the top surface will follow the curve and give a more accurate reading than a rigid ruler, which would cut across it.
How to Measure Girth
Girth is the circumference, the distance around the shaft. Wrap a soft measuring tape snugly around the thickest part of the shaft, typically just below the head. Don’t pull the tape tight enough to compress the skin, but don’t leave it loose either. Read the number where the tape meets itself.
If you don’t have a flexible tape, use a piece of string or a strip of paper. Wrap it around the thickest point, mark or pinch where the ends overlap, then lay the string flat against a ruler to get the measurement. This string method is just as accurate as a tape measure when done carefully.
Getting a Consistent Reading
Erection quality matters. A partial erection will give you a shorter and thinner measurement than a full one, so take your measurement when you’re at maximum rigidity. If your erection fluctuates, measure a few times on different days and use the average. Room temperature, arousal level, and even time of day can cause slight variation, so don’t read too much into a single measurement.
Measure along the top of the shaft (the side facing your belly button), not the underside. The underside includes extra tissue near the scrotum that inflates the number and doesn’t match how clinical measurements are taken.
How You Compare to Averages
A large review published in BJU International pooled data from over 15,500 men and found the following averages:
- Erect length: 13.12 cm (about 5.16 inches)
- Erect girth: 11.66 cm (about 4.59 inches)
- Flaccid length: 9.16 cm (about 3.61 inches)
- Flaccid girth: 9.31 cm (about 3.67 inches)
Most men fall within roughly an inch above or below those numbers. Flaccid size is a poor predictor of erect size. Some men grow substantially when erect while others are closer to their final size even when soft.
A micropenis is a clinical diagnosis reserved for measurements that fall more than 2.5 standard deviations below the mean, which works out to an erect length under about 3 inches in adults. This is rare and typically identified in infancy.
Using Your Measurements for Condom Fit
The main reason to know your girth is condom sizing. Condoms are categorized by “nominal width,” which is the width of the condom opening when laid flat. To find yours, divide your girth measurement by 3.14. So if your girth is 5 inches, your width is about 1.59 inches (roughly 40 mm).
Here’s how nominal widths map to condom sizes:
- Small / Snug: 49 to 52 mm
- Regular / Standard: 52 to 56 mm
- Large: 56 to 60 mm
- Extra-Large: 60 to 64 mm
A condom that’s too tight is more likely to break, and one that’s too loose is more likely to slip off. Getting the right fit based on your actual girth measurement makes a real difference in both comfort and reliability. Length matters less for sizing since most condoms can be unrolled only as far as needed, but if a standard condom consistently bunches up at the base, a shorter or “fitted” option may work better.