I have a mix of ages and sizes here so this is an average of everyone...but I feed 15 cats ranging from my youngsters at 5lbs and just barely over a year or two old to my big kids at 16, 17, and 14 lbs and ranging in age from 13-18 years old on 20 (5.5 oz) cans per day. The big guys get about a can and a half, while the little ones get about 6 ounces a day, the kitten slightly more at about 8-10 ounces but she is normally bouncing around the house like she's on springs, the rest are between 6-18 and are far less active. Now I have some that are long and lean in body frame (Siamese & Orientals) as well as some that are big linebacker body types so it takes knowing your own cat's ideal body type and adjusting the food accordingly. On Autumn that we suspect has a lot of Maine Coon in her family tree @ 5 lbs she was a walking skeleton, but that same 5 lbs on my little petite dainty meezer girl Arabella she is well a bit 'fluffy' around the middle.
Need to gain weight feed more, need to take the pounds off feed less.
Mel and The Fur Gang