How the calculator works

It starts from the time you want to carve and serve, then works backwards one step at a time using the USDA Food Safety and Inspection Service (FSIS) figures:

Resting: FSIS says to let the turkey stand for 20 minutes before carving, so it comes out of the oven 20 minutes before dinner.
Roasting: FSIS gives a range of hours for each weight at 325°F (163°C). The calculator plans with the long end of the range so dinner isn't late, and tells you to start checking the temperature once the short end has passed. FSIS's rows share their end weights (8 to 12 lb, 12 to 14 lb), so a weight right on the line, such as 12 lb, uses the lighter row; the two rows' times meet there.
Prep: your own estimate of the time between taking the turkey out of the fridge and putting it in the oven. The oven goes on at the start of it. It is limited to 2 hours, because FSIS says perishable food must not be left at room temperature for more than 2 hours.
Thawing: in the fridge FSIS allows about 24 hours for every 4 to 5 pounds; the calculator uses the slower 4 pounds a day, and never less than a day. In cold water it allows about 30 minutes per pound. From frozen, roasting takes at least 50% longer, so the roasting range is multiplied by 1.5.
Clock changes: times are counted in real hours in your own time zone, so if the clocks change during a long fridge thaw, the start time still comes out right.

Worked example

Say you want to eat at 4:00 pm on Thanksgiving, Thursday, November 26, 2026, with a 14 lb turkey that is not stuffed, thawed in the fridge, and you allow 30 minutes for prep.

Out of the oven: 20 minutes before dinner, at 3:40 pm.
Roasting: FSIS gives 3 to 3¾ hours for 12 to 14 lb. Planning with 3 h 45 min puts the turkey in the oven at 11:55 am. Start checking the temperature 3 hours in, at 2:55 pm. If it went in after 12:40 pm, even the short end of the range would make dinner late.
Prep: oven on and turkey out of the fridge at 11:25 am.
Thawing: 14 lb at 4 lb a day is 3.5 days (84 hours), so the turkey goes into the fridge by 11:25 pm on Sunday, November 22. At the faster 5 lb a day (2.8 days) it could be thawed by 6:37 pm on Wednesday, which is fine: FSIS says a thawed turkey can stay in the fridge for 1 to 2 days.

Thawing in cold water instead, 14 lb at 30 minutes a pound is 7 hours, so you would start at 4:25 am on Thursday. Cooking from frozen, the roast takes at least 4 h 30 min to 5 h 38 min, so the turkey would go in at 10:02 am.

FSIS roasting times at 325°F (163°C)

Turkey	Weight	Not stuffed	Stuffed
Turkey breast	4 to 6 lb (1.8 to 2.7 kg)	1½ to 2¼ hours	Not usually applicable
Turkey breast	6 to 8 lb (2.7 to 3.6 kg)	2¼ to 3¼ hours	2½ to 3½ hours
Whole turkey	8 to 12 lb (3.6 to 5.4 kg)	2¾ to 3 hours	3 to 3½ hours
Whole turkey	12 to 14 lb (5.4 to 6.4 kg)	3 to 3¾ hours	3½ to 4 hours
Whole turkey	14 to 18 lb (6.4 to 8.2 kg)	3¾ to 4¼ hours	4 to 4¼ hours
Whole turkey	18 to 20 lb (8.2 to 9.1 kg)	4¼ to 4½ hours	4¼ to 4¾ hours
Whole turkey	20 to 24 lb (9.1 to 10.9 kg)	4½ to 5 hours	4¾ to 5¼ hours

FSIS says these times are approximate, and lists many things that change them: a partly frozen or stuffed bird takes longer, oven thermostats can be inaccurate, dark pans cook faster than shiny ones, a lid or an oven bag speeds cooking and a foil tent left on the whole time slows it. The times are for a fresh or fully thawed bird kept in a fridge at 40°F (4°C) or below, roasted on a rack in a shallow pan. The kilogram figures are conversions of FSIS's pounds. FSIS's table stops at 24 lb, so the calculator does not guess times for bigger turkeys.

Thawing times

Weight	In the fridge	In cold water
4 to 12 lb (1.8 to 5.4 kg)	1 to 3 days	2 to 6 hours
12 to 16 lb (5.4 to 7.3 kg)	3 to 4 days	6 to 8 hours
16 to 20 lb (7.3 to 9.1 kg)	4 to 5 days	8 to 10 hours
20 to 24 lb (9.1 to 10.9 kg)	5 to 6 days	10 to 12 hours

These are FSIS's rows. For your exact weight the calculator uses the two rules FSIS gives with them: about 24 hours per 4 to 5 lb in a fridge at 40°F (4°C) or below, and about 30 minutes per pound in cold water. FSIS's Big Thaw guide adds that food thaws more slowly in a fridge set at 35°F than at 40°F, so start earlier if your fridge runs cold. FSIS also lists the microwave as a safe way to thaw: check your oven's manual for the size of turkey that fits and the settings, and cook the turkey straight afterwards. The calculator doesn't plan microwave thawing because the times depend on the oven.

Food safety rules from FSIS

Never thaw a turkey on the counter. FSIS says perishable food should never be thawed on the counter or in hot water, nor in a garage, basement, car or outdoors. Even if the middle is still frozen, the outside can sit in the "Danger Zone" of 40°F to 140°F (4°C to 60°C), where bacteria multiply quickly.
Fridge thawing: keep the turkey in its original wrapper on a tray or in a pan to catch drips. Once thawed it can stay in the fridge for 1 to 2 days before cooking, and it can be refrozen, with some loss of quality.
Cold-water thawing: use a leak-proof bag, submerge it in cold tap water and change the water every 30 minutes. Cook the turkey immediately after it thaws, and don't refreeze it raw.
Giblets: take them out of the cavities after thawing and cook them separately.
Stuffing: FSIS does not recommend stuffing a turkey; for the safest, most even result, bake the stuffing in a casserole. If you do stuff it, mix the wet and dry ingredients just before filling the bird, fill it loosely and cook it straight away. The centre of the stuffing must reach 165°F (74°C) as well as the meat, so keep cooking if the stuffing is behind. Let the bird stand 20 minutes before removing the stuffing.
Pre-stuffed turkeys: FSIS says not to buy a fresh pre-stuffed turkey. Cook a commercially frozen pre-stuffed turkey from frozen, without thawing, following the package directions. If one has thawed completely in the fridge, FSIS says to throw away both the turkey and the stuffing.
Check with a food thermometer: a whole turkey is safe at 165°F (74°C) in the innermost part of the thigh and wing and the thickest part of the breast; for a turkey breast, check its thickest part. FSIS advises checking even if the turkey has a pop-up indicator.
Leftovers: throw away turkey, stuffing and gravy left at room temperature for more than 2 hours (1 hour above 90°F, 32°C). Refrigerate leftovers in shallow containers and use them within 3 to 4 days.

Outside the US

Guidance differs between countries. The UK Food Standards Agency's own defrosting and roasting rules are in the questions below. Health Canada's cooking temperature chart lists 82°C (180°F) for whole poultry and 74°C (165°F) for poultry pieces and for stuffing. Wherever you are, follow the instructions on your turkey's packaging and your national food safety agency first.

Common questions

How long does a 20 lb turkey take to thaw?: In the refrigerator, FSIS says to allow about 24 hours for every 4 to 5 pounds, so a 20 lb turkey needs 4 to 5 days; the calculator plans for the slower 5 days. In cold water it takes about 30 minutes per pound, so about 10 hours, changing the water every 30 minutes. A turkey thawed in cold water must be cooked straight away.
How long does a 20 lb turkey take to cook?: At 325°F, FSIS gives 4¼ to 4½ hours for an unstuffed turkey of 18 to 20 lb, and 4¼ to 4¾ hours if it is stuffed. 20 lb is where two rows meet, and FSIS's 20 to 24 lb row starts at 4½ hours. The times are approximate: the turkey is done when a food thermometer reads at least 165°F in the innermost part of the thigh and wing and the thickest part of the breast, and in the centre of any stuffing. Then let it stand for 20 minutes before carving.
Can I cook a turkey that is still frozen?: Yes. FSIS says it is safe, but it takes at least 50 percent longer. A 14 lb unstuffed turkey that needs 3 to 3¾ hours when thawed needs at least 4 h 30 min to 5 h 38 min from frozen. Take the giblet packages out during cooking, carefully, with tongs or a fork. The calculator does not plan stuffed turkeys from frozen: for a commercially frozen pre-stuffed turkey, FSIS says to cook it from frozen without thawing and follow the package directions.
How big a turkey do I need?: FSIS suggests allowing 1 pound of turkey per person, or 1¼ pounds for a frozen pre-stuffed turkey. So 12 people need about a 12 lb (5.4 kg) turkey. The "How big a turkey?" box in the calculator works it out and can copy the weight into the form.
I am in the UK. Is the advice different?: Yes. The UK Food Standards Agency says to follow the instructions on the packaging first. If there are none, it says to defrost the turkey in the fridge, never at room temperature, allowing around 10 to 12 hours per kg, and notes that a typical 6 to 7 kg turkey could take as much as 4 days. To roast it, it says to use an oven preheated to 180°C (160°C fan, 350°F, Gas Mark 4) for 45 minutes per kg plus 20 minutes under 4.5 kg, 40 minutes per kg from 4.5 to 6.5 kg, and 35 minutes per kg over 6.5 kg. So a 6 kg turkey needs 60 to 72 hours in the fridge by the per-kg rule and about 4 hours in the oven. The FSA also says to cook the stuffing in a separate tin, not inside the turkey. To check it is cooked, cut into the thickest part, between the leg and the breast: it should be steaming hot, with no pink meat and juices running clear. With a temperature probe, the thickest part must reach one of the FSA's time and temperature pairs, such as 75°C for 30 seconds or 70°C for 2 minutes. This calculator uses the US FSIS times.

Sources

Last checked and updated: November 1, 2026.