
Bianca Piper is best friends with two of the popular girls in high school and is content with her ignorance of her place in the social pecking order, until her childhood friend and jock Wes (Robbie Amell) reveals to her at a party that she is the "DUFF" (Designated Ugly Fat Friend) of her group. She's the one that people approach because they feel more comfortable using her for information to find out about her friends. Insulted and no longer oblivious, noticing DUFFs in every social group, Bianca eventually strikes a deal with Wes to help her become more popular and to talk to her crush Toby (Nick Eversman) in return for tutoring him in Chemistry.
The two start to reform a friendship as Wes takes Bianca shopping and instructs her on social interaction with boys, but it's cut short when mean girl Madison (Bella Thorne) finds out about Bianca hanging out with Wes, her on-again-off again ex-boyfriend and makes it her mission to destroy her life.