Rangers have won just twice in the league and are seven points behind fourth-bottom Aston Villa with 12 games to play.
And Redknapp, whose side are bottom on 17, has spelt out in stark terms the size of the task ahead.
He told the club website: "I think we need 20 points from our final 12 games to give ourselves a chance, to be honest.
"If someone offered me 37 points now I'd probably take my chance and think that would be enough."
Next up for QPR is a game against leaders Manchester United at Loftus Road, where Tottenham and Manchester City have both failed to win since the turn of the year.
Redknapp said: "Welcoming United to Loftus Road is something I'm sure the fans are excited about.
"We know it's going to be a tough game, but it's a great challenge for us."