The first thing to consider when planning when to put the turkey in the oven is the stuffing. A stuffed turkey takes longer to cook than an unstuffed turkey. Assuming you are roasting your turkey in a 325°F oven, plan on 15 to 17 minutes of cooking time for each pound of an unstuffed turkey. Plan on 20 to 22 minutes per pound for a stuffed turkey.
What that means on the real world of your kitchen is this for an unstuffed turkey:
Keep in mind that the times are approximate. The best way to know when your turkey is cooked is to take its temperature with either a quick-read thermometer or a meat thermometer. When the thermometer is inserted into the thickest part of the thigh but not touching the bone, the turkey is done when the temp reaches 180°F. in addition, the thigh and drumstick meat should feel soft when pressed, and when the thigh is pierced with a fork the juices should run clear, not pink. If you have stuffed the turkey, be sure to check the temp on the stuffing, too. It should register 165°F in the center.
All of the above information is for a standard oven. If you are using a convection oven, be sure to check the temperature of your turkey an hour before the recommended time: It will cook faster, and you don’t want an overcooked bird.