A roast cooking time calculator by weight, built on USDA timetables
Most roasts come with a weight on the label and a recipe that assumes a different one. This cooking time calculator by weight takes the bird or joint you actually have, in kilograms or pounds, and gives a roasting time range, the oven setting in °F, °C, fan and gas mark, the temperature to look for on a thermometer and how long to rest it.
Every time comes from the US Department of Agriculture Food Safety and Inspection Service (FSIS), whose roasting timetables are the only official ones we know of. The tool multiplies the FSIS minutes per pound by your weight, uses the FSIS totals for birds, and says plainly when your weight is outside the published range. The clock gets you close; the thermometer tells you when it is done.
How to use the Roast Cooking Time Calculator by Weight
- Choose what you are roasting: the list is grouped into poultry, beef, lamb, pork, gammon and cooked ham, and veal.
- Enter the weight from the label and pick kg or lb. Switching the unit converts the number for you.
- For beef and lamb, choose your doneness to see when to take it out of the oven. For birds, tick stuffed if you will stuff it.
- Tick roasting from frozen if the meat is still frozen; FSIS says this takes at least half as long again.
- Read the time range, start checking at the time shown, and cook to the safe internal temperature. Copy the result if you want it in a note.
Roast Cooking Time Calculator by Weight features
Kilograms or pounds
Weights in either unit, with the conversion shown next to every FSIS row, so UK and Indian cooks can use the US tables directly.
Thirty-four cuts
Poultry, beef, lamb, pork, veal, gammon and fully cooked ham, each from a named FSIS chart.
Honest ranges
Low and high times rounded to 5 minutes, with interpolation between FSIS weight bands and a warning outside them.
Safety first
USDA safe minimum internal temperatures on every result, plus the UK Food Standards Agency advice for the same meat.
Doneness pull temperatures
Rare to well done for beef and lamb, with carry-over allowed for, as in our meat doneness chart.
Safe internal temperatures (USDA FSIS)
Cook to these temperatures, measured with a food thermometer in the thickest part of the meat and away from bone, before you take the food off the heat. The FSIS chart was last updated in April 2025.
| Food | Minimum internal temperature |
|---|---|
| Beef, pork, veal and lamb roasts, steaks and chops | 145 °F (63 °C), then rest at least 3 minutes |
| Ham, fresh or smoked, uncooked (gammon) | 145 °F (63 °C), then rest at least 3 minutes |
| Fully cooked ham, reheated | 140 °F (60 °C) if packaged in a USDA-inspected plant, otherwise 165 °F (74 °C) |
| All poultry, including stuffing | 165 °F (74 °C) |
| Minced meat (burgers, meatloaf) | 160 °F (71 °C) |
How the times are calculated
For joints, FSIS publishes minutes per pound for a weight range, for example 23 to 30 minutes per pound for a 4 to 8 lb bone-in rib of beef at 325 °F. A 6 lb rib therefore needs 138 to 180 minutes, which the tool rounds to 2 h 15 min – 3 h. Whole chickens and turkeys are published as total times for a weight band instead: a 3 to 4 lb chicken roasts in 1¼ to 1½ hours at 350 °F. When your weight falls between two bands, the tool interpolates; outside them it scales from the nearest row and says the answer is rough.
Boned and rolled joints take longer per pound than bone-in ones because heat has further to travel through solid meat. Ovens run hot or cold and a joint straight from the fridge takes longer, so every result is a range. To roast at a different oven temperature, try the cooking time adjuster.
Turkey, gammon and the rest of the meal
For a frozen turkey, the turkey thawing calculator plans the days of thawing as well as the roast, and the defrost time calculator handles other joints. Gammon is raw cured pork, which FSIS calls a cook-before-eating ham; a cooked ham only needs reheating. To get the potatoes and vegetables ready at the same time, back-time the whole dinner with the meal timing planner, and check doneness temperatures in the meat doneness chart.
Roast Cooking Time Calculator by Weight FAQ
How long does it take to cook a chicken per kg?
FSIS gives 1¼ to 1½ hours at 350 °F (180 °C) for a whole 3 to 4 lb (1.4–1.8 kg) chicken, and 2 to 2¼ hours for a 5 to 7 lb (2.3–3.2 kg) roasting hen. A 2 kg bird falls between those rows, at about 1 h 30 min – 1 h 50 min. It is done at 165 °F (74 °C) in the thickest part of the breast and thigh.
How long do I cook a leg of lamb by weight?
A bone-in leg takes about 20 to 26 minutes per pound at 325 °F (160 °C), so a 2.5 kg (5.5 lb) leg needs roughly 1 h 50 min – 2 h 25 min. A boneless rolled leg takes 25 to 30 minutes per pound. Take it out at 145 °F (63 °C) for the USDA minimum, or earlier if you like it pink.
How long does a gammon joint take to cook?
Gammon is a cook-before-eating ham. FSIS gives 35 to 40 minutes per pound at 325 °F for small boneless and shank joints, so a 1.5 kg (3.3 lb) joint takes about 1 h 55 min – 2 h 15 min. Cook it to 145 °F (63 °C) and rest it for at least 3 minutes; UK advice is to cook it until there is no pink juice and it is steaming hot.
How do I work out ham cooking time by weight?
Multiply the weight in pounds by the FSIS minutes per pound for your ham. A fully cooked spiral-cut ham reheats in 10 to 18 minutes per pound at 325 °F to 140 °F (60 °C); a whole cook-before-eating ham takes 18 to 20 minutes per pound to 145 °F.
Should I trust the time or the thermometer?
The thermometer. FSIS calls its timetables approximate and for planning only. Start checking at the time shown and keep roasting until the safe internal temperature is reached in the thickest part.
Can I roast meat from frozen?
Yes. FSIS says it is safe but takes at least 50 percent longer, which this tool adds when you tick the box. Do not stuff a frozen bird; cook the stuffing separately.