How to measure your penis length - erect
To measure the erect length of your penis, you're going to use the straight ruler.
While as erect as possible, place the flat edge of the ruler against the top side of the penis with the ZERO at your base. To accurately measure, now take the measurement from the very tip of your penis while the penis is as close to 90 degrees as possible.
Bone pressed vs non bone pressed - The pubic bone
Between your skin and pubic bone, you have what is called a pelvic fat pad. You may choose to measure with the ruler pressed into this or not.
Pressing in and pushing the ruler hard enough into your fat pad, until you feel the ruler resting on your pubic bone, is considered your bone pressed erect length.
Taking the measurement with the ruler softly resting against the skin of the pelvic fat pad is considered your non-bone pressed erect length.
If you are comparing to the worldwide average penis sizes, it's best to measure non-bone pressed.
How to measure penis girth - erect
Measuring the erect girth of your penis is going to require something like a flexible tape measure or soft measuring tape.
Alternatively, you can use a flexible material that you can measure against the straight ruler.
While erect, if comparing to the worldwide average, you should measure penis girth near the base of your penis.
Wrap the tape around the shaft and take the measurement from where the measuring tape meets itself again, while only applying a moderate amount of pressure to the tape (tightness).
If using something else, like a cord or string, wrap around the circumference of the shaft and grab the cord or string where it meets itself. While holding that position with your fingers, measure it straightened out against the straight ruler.