The two categories of young adult literature — young adult (YA or "teen fiction") and middle grade ("MG fiction") — are split into several age ranges to help book buyers and readers judge the age-appropriateness of the content and the writing. The shift from tween to teen begins around age 12, and standard age ranges reflect that.
| Middle Grade (MG) 25,000 to 45,000 words |
Ages 9 to 12 | Older elementary into middle school, grades 4 through 7 |
| Ages 10 to 14 | Middle school into early high school, grades 5 through 9; these kids may be reading older MG and younger YAs | |
| Young Adult (YA) 40,000 to 60,000 words |
Ages 12 and up | Older middle school into high school, grades 7 through 12 |
| Ages 14 and up | High school, grades 9 and up; generally understood to cap at age 17 |
