Measure when the penis is fully erect
Use a rigid ruler or measuring tape
Place the ruler on the top side of the penis
Press the ruler firmly into the pubic bone
Measure from the pubic bone to the tip of the glans
Do not include the foreskin beyond the tip
Keep the penis parallel to the floor for consistency
Measure in the same position each time
Record the length in inches or centimeters
For flaccid length, use the same top-side, pubic-bone-to-tip method