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.
1. Sheffield United player ratings
Sander Berge celebrates his goal. Photo: Danny Lawson
2. Wes Foderingham - 8
Had little to do all afternoon but made three top saves to keep Fulham at bay, including one on the stroke of half time, which would have given the Cottagers a lifeline in the match. Photo: Andrew Yates
3. Ben Osborn - 7
Industrious display on the left-hand side and got forward at every opportunity. Photo: Adam Davy
4. Chris Basham - 7
Solid throughout. Enough said. Photo: David Klein