The most widely accepted rule for cooking a turkey is to plan on 20 minutes per pound at 350 degrees Fahrenheit. This will vary based on whether the turkey is stuffed or unstuffed. A turkey should be roasted until a meat thermometer inserted into the breast reaches 165 degrees Fahrenheit.
When cooking a stuffed turkey, plan on the roasting process to take longer. A turkey that is loosely stuffed will cook more evenly than a tightly stuffed turkey. A meat thermometer inserted into a thigh should read 180 degrees Fahrenheit when the turkey has completed cooking. When roasting a stuffed turkey, the stuffing should reach 165 degrees Fahrenheit before the turkey is removed from the oven.