A 3-ounce chicken breast cooked is about the size of a deck of cards. The same goes for three ounces of cooked lean beef. A 1/4 cup of almonds is about the size of a golf ball while 1 ounce of luncheon meat is the size of a compact disc. {relatedarticles}A bagel should be the size of a can of tuna - a slice of bread the size of a cassette tape. A one-cup serving of cooked pasta should be about the size of baseball. A 1/2 cup serving of cooked rice is about the size of a light bulb. One your portions start expanding beyond these basic estimates, remember, your waistline may quickly follow. Measure out your food so you don't exceed your recommended daily caloric intake.