A 9- to 12-pound turkey comfortably feeds six people. A general rule suggests an allotment of 1 to 2 pounds of turkey for each adult and a 1/2 pound of turkey for each child.
Martha Stewart suggests 1 1/2 pounds of turkey per person if the turkey is 15 or more pounds. When the turkey is 12 pounds or less, Stewart suggests increasing serving sizes to 2 pounds of turkey per person to account for lower meat-to-bone ratio.
Online portion calculators are tools to help determine what size turkey to buy for various assortments of guests. The calculator on Butterball.com offers portion suggestions according to the number of children and adult guests, whether the guests are big or light eaters, and whether or not the host prefers leftovers.