How much should you be able to bench press if you are a 18-year old boy?

it depends on your body build. in a general statement at 18 years old...

How Much You Way-How Much You should Lift.

120-25/35

130-30/40

140-30/45

150-35/45

160-40/50

170+55&up

(excluding bar) (& weight on each side, not combined. ex. 45=45 on each side)