To measure a curved penis accurately, use a flexible measuring tape instead of a rigid ruler. The tape follows the contour of the curve along the top of the shaft, giving you the true functional length rather than an artificially shortened straight-line number. If you also want to know the degree of curvature itself, that requires a different approach involving photos and a protractor or smartphone app.
Measuring Length With a Flexible Tape
A rigid ruler measures the straight-line distance between two points, which shortchanges anyone with a noticeable curve. A soft fabric or plastic measuring tape conforms to the bend, capturing the full length from base to tip. This is the single most important adjustment for an accurate measurement.
Start while fully erect, since a partial erection will give an inconsistent result. Place the end of the tape where the top of the shaft meets the pubic bone, pressing gently inward against the bone to account for any padding from the fat pad above the penis. This “bone-pressed” technique is the standard used in most clinical studies and gives the most reproducible number. Run the tape along the topside of the shaft, following the curve, all the way to the tip of the glans. Read the measurement where the tape meets the tip.
If you don’t have a flexible tape, a piece of string works. Lay it along the same path, mark where the tip falls, then measure the string flat against a ruler.
Measuring Girth
Wrap the flexible tape or a piece of string around the thickest part of the shaft while erect. For most people, this is somewhere around the midshaft. If your penis has a noticeable narrowing or indentation (sometimes called an hourglass shape), there is no universally validated clinical method for quantifying that precisely. Even specialists sometimes describe such narrowing qualitatively as mild, moderate, or severe rather than relying on a number. For a general girth measurement, the widest point is the standard reference.
Measuring the Degree of Curvature
Length and girth tell you size. The curve itself is measured in degrees. Knowing this number is especially useful if you’re tracking changes over time or preparing for a conversation with a urologist about Peyronie’s disease.
The most practical at-home method uses photographs and a protractor (physical or digital). While fully erect, take a photo of your penis from the side (for upward or downward curves) or from above (for left or right curves). Hold the camera at a 90-degree angle to the direction of the bend so the full curve is visible in one plane. The American Urological Association recognizes home photography with a protractor as a valid way to document curvature.
On the photo, imagine or draw a straight line through the center of the base (proximal) portion of the shaft. Draw a second straight line through the center of the portion beyond the bend, extending toward the tip. The angle where those two lines intersect is your curvature in degrees. A basic protractor held up to a printed photo, or a free protractor app used on the image, will give you the number.
Three-Photo Technique
A method introduced in 1983 by urologist Kelâmi, and still widely used, involves taking three photos of the erect penis: one from above (craniocaudal), one from the side (lateral), and one from the front (frontal). This captures curves that bend in more than one direction. A single photo can miss part of a complex curve. A side shot reveals upward or downward bending well but won’t show a lateral component, while a top-down shot does the opposite. All three together give you (or your doctor) the full picture.
Smartphone Apps for Angle Measurement
Researchers at the University of Washington developed an app called UWPEN specifically for measuring penile curvature from photos. In validation testing, its angle measurements were essentially identical to those taken with a physical goniometer or protractor, with near-perfect agreement across different users, including non-physicians. If you prefer a digital approach, a curvature-measurement app removes the guesswork of holding a protractor to a photo. Automated image-analysis tools are also in development, with early versions achieving a mean error of about 8.5 degrees compared to expert measurements.
Common Mistakes That Skew Results
The biggest source of error is measuring without a full erection. Even slight softness changes both the apparent length and the angle of the curve, typically making the curvature look less severe than it actually is. Underestimation is far more common than overestimation.
Positioning the protractor or drawing the reference lines in slightly different spots introduces variability of 5 to 10 degrees, even when the same person measures repeatedly. That’s inherent to the process, not a mistake you can fully eliminate. To minimize it, take multiple measurements on different occasions and look at the average.
Photos can also be misleading when the curve bends in more than one direction. A two-dimensional image flattens a three-dimensional shape, so a complex curve with both lateral and dorsal components will look less severe in any single photo. Narrowing or indentation of the shaft is particularly hard to capture on camera. This is why the three-angle photo set matters: it reduces the chance that you’ll miss a component of the deformity.
When Tracking Changes Over Time
If you’re monitoring a curve that seems to be progressing, consistency matters more than precision. Use the same measurement method, the same camera angle, and the same level of erection each time. A 5-to-10-degree shift between two measurements taken differently doesn’t necessarily mean anything changed. A 15-to-20-degree shift measured the same way both times almost certainly does. Keeping a dated photo log gives you and any future clinician a reliable timeline to work with.