Magath steered his club to their maiden German league title in 2009 before joining Schalke 04 but he returned to Wolfsburg towards the end of last season.
"The last time [in 2009] it took two years to do it. Now the situation is a bit harder. So we should add a year to that," he told Sport1 broadcaster.
Wolfsburg are 11th in the Bundesliga on 13 points after 10 matches, nine adrift of leaders Bayern Munich.
"Now it will be starting to go up with Wolfsburg," the 58-year-old said.
"Then we will also make the Champions League at some point and then we will see if the end there will be in the semi-finals or if we will advance a step further than that."
It is not the first time Magath, who also won the Bundesliga twice as Bayern Munich coach, has set tough targets for his team.
When he joined Schalke in 2009 he pledged to win their first ever Bundesliga title within four seasons.
He helped them finish second and took them to the Champions League quarter-finals last season before being sacked. Schalke went on to reach the semi-finals under new coach Ralf Rangnick.
