Preparing Thanksgiving dinner is enough of a pressure cooker, never mind having to do on-the-fly math to get it right. Here are all the numbers you need to have a safe, worry-free and delicious Turkey Day dinner.

All serving estimates are generous to allow for plenty of seconds and leftovers.

HOW BIG?

For turkeys under 16 pounds, estimate 1 pound per serving (this accounts for bone weight). For larger birds, a bit less is fine; they have a higher meat-to-bone ratio. But if your goal is plenty of leftovers, aim for 1 1/2 pounds per person whatever the turkey's size.

Ÿ For 8 people, buy a 12-pound turkey

Ÿ For 10 people, buy a 15-pound turkey

Ÿ For 12 people, buy an 18-pound turkey

Ÿ For 14 people, buy a 20-pound turkey

THE BIG THAW?

The safest way to thaw a frozen turkey is in the refrigerator. You'll need about 24 hours per 4 to 5 pounds of turkey. You also can put the turkey in a sink of cold water. Change the water every 30 minutes, and plan for about 30 minutes per pound.

THE BRINE

Never brine a turkey for more than about 8 to 10 hours. Much longer and the meat will be too salty. Always keep the bird refrigerated during brining. If the turkey is too big, an ice-filled cooler stored outside is fine, too.

THE ROAST

Roasting temperatures vary widely by recipe. Some go at a slow and steady 325 F. Others crank the heat to 400 F or 425 F for the first hour, then drop it down for the rest of the time.

However you roast, use an instant-read thermometer inserted at the innermost part of the thigh (without touching bone) to determine when your turkey is done. The meat needs to hit 165 F for safe eating, though some people say thigh meat tastes better at 170 F.

The following roasting time estimates are based on a stuffed turkey cooked at 325 F. Reduce cooking time by 20 to 40 minutes for turkeys that are not stuffed. And remember, a crowded oven cooks more slowly, so plan ahead if your bird needs to share the space.

Ÿ 12-pound turkey: 3 to 4 hours at 325 F

Ÿ 15-pound turkey: 4 to 4 1/2 hours at 325 F

Ÿ 18-pound turkey: 4 1/2 to 5 hours at 325 F

Ÿ 20-pound turkey: 5 to 6 hours at 325 F

THE REST

The turkey should never go directly from the oven to the table. Like most meat, it needs to rest at least 20 minutes.

THE SIDES

Ÿ Carrots: a 1-pound bag makes 4 to 5 servings

Ÿ Cranberry sauce: a 12-ounce package of fresh cranberries makes about 2 cups of sauce; a 16-ounce can has 6 servings

Ÿ Gravy: plan for cup of gravy per person

Ÿ Green beans: 1 1/2 pounds makes 6 to 8 servings

Ÿ Mashed potatoes: a 5-pound bag of potatoes makes 10 to 12 servings

Ÿ Stuffing: a 14-ounce bag of stuffing makes about 11 servings