Why don't you see No. 1 or No. 3 pencils on your back-to-school checklist? Here's why the No. 2 is the Goldilocks of writing utensils.

No. 1 pencils were the darkest; No. 2 were the second darkest, and so on. Today, that scale includes 21 different grades, but No. 2 pencils are still the ultimate “tweener” pencil: ...

The number on the pencil indicates the degree of how hard the graphite is. Pencils with lower numbers are easier to erase but don't smudge as easily. That's why the No. 2 pencil is used on test ...

In all likelihood, if you rummaged through any given school desk in the U.S., the first pencil you'd encounter would be a number two pencil. Here's why. The United States tends to do its own thing ...

For the purposes of a test, a No. 1 pencil is a little too soft, and smudges easily; as you get higher in number, the lead becomes too dense and brittle to write and erase easily.