The right amount of reps and sets depends on your goals. There are tons of variations that produce results. Generally, the following guidelines will set you up for success:  For strength: 1 to 5 reps at 80% of one-rep max For hypertrophy (muscle growth): 6 to 12 reps at 60 to 75% one-rep max For muscular endurance: 15 or more reps at 40 to 50% one-rep max