First half goals from Morgan Gibbs-White, Iliman Ndiaye and Sander Berge put the Blades in cruise control inside the opening 30 minutes before Enda Stevens got in on the action after the break.
The win means United will play Nottingham Forest in the play-off semi-final.
Steve Cooper’s side drew 1-1 against Hull City this afternoon.
The first leg will take place at Bramall Lane next Saturday with the return fixture on Tuesday 17 May.
Here’s our player ratings after a brilliant afternoon.
5. John Egan - 8
Aleksandar who? Kept the division's best player so quiet he was replaced on the hour mark. Also saw a header cleared off the line in the second period. Photo: Adam Davy
6. Jack Robinson - 7
Played his part in keeping Fulham quiet throughout. Photo: David Klein
8. Ollie Norwood - 8
Provided a pinpoint cross for the opener and was on point with his set pieces throughout. Photo: David Klein