A square inch is calculated as the area of a square that has 1 inch on each side.
You've also probably wondered how your penis size compares to other people's because—unfortunately—we live in a society that assigns a ridiculous amount of importance to the size of a person's schlong.
The inch is still commonly used informally, although somewhat less, in other Commonwealth nations such as Australia; an example being the long standing tradition of measuring the height of newborn children in inches rather than centimetres.
The distance between any two large numbered lines is 1 inch.
Centimeter value will be converted automatically as you type.
If your partner wants you to go deeper, of course, listen to them, but you really want to start off slow and gentle.