McKellar studied at the University of California, Los Angeles where she was a member of the Alpha Delta Pi sorority and earned a Bachelor of Science degree summa cum laude in Mathematics in 1998. She is of paternal Scottish, French, German, Spanish, and Dutch descent and her mother is of Portuguese origin via the Azores and Madeira islands. Her mother Mahaila McKellar (née Tello) was a homemaker her father Christopher McKellar is a real estate developer her younger sister Crystal (b. She moved with her family to Los Angeles when she was eight. McKellar was born in La Jolla, California. In addition to her acting work, McKellar later wrote six non-fiction books, all dealing with mathematics: Math Doesn't Suck, Kiss My Math, Hot X: Algebra Exposed, Girls Get Curves: Geometry Takes Shape, which encourage middle-school and high-school girls to have confidence and succeed in mathematics, Goodnight, Numbers, and Do Not Open This Math Book. She is the current voice of Judy Jetson from The_Jetsons_&_WWE:_Robo-WrestleMania! since 2017 following Janet Waldo's death the previous year. She appears in several television films for Hallmark Channel.

In 2015, McKellar was cast in the Netflix original series Project Mc 2. She played Winnie Cooper in the television series The Wonder Years from 1988 to 1993, and from 2010 to 2022, has voiced Miss Martian in the animated superhero series Young Justice. Danica Mae McKellar (born January 3, 1975) is an American actress, mathematics writer, and education advocate.

Finding Home by Lauren K. McKellar