Use a soft measuring tape or a ruler
Measure when the penis is fully erect for length
Place the ruler along the top side of the penis
Start at the pubic bone, pressing gently into the fat pad
Measure to the tip of the glans
For girth, wrap the measuring tape around the thickest part of the shaft
Record the circumference where the tape meets
Measure in a warm, private setting
Repeat the measurement a few times and use the average
If needed, compare results with a healthcare professional