Roast Cooking Time Calculator

About the Roast Cooking Time Calculator

A Sunday roast is one of the simplest meals to prepare and one of the easiest to get wrong. The joint goes into the oven and there is nothing to see until it comes out — pink and juicy, or grey and dry. Cooks have long relied on a simple rule of thumb, a set number of minutes per pound or per 500 grams plus a little extra, and it still works well as a starting point.

This roast cooking time calculator works out how long to roast beef, lamb, pork or a whole chicken by weight, in kilograms or pounds. For beef and lamb, choose rare, medium or well done. It gives the cooking time, the oven temperature, the internal temperature to take the meat out at, the resting time, and the setting for a fan oven.

How to Use the Roast Cooking Time Calculator

Choose the meat.

Enter the weight of the joint and choose kg or lb.

For beef or lamb, choose the doneness you want.

How the Cooking Time Is Worked Out

  time  =  (weight ÷ 500 g) × minutes per 500 g  +  the same minutes again

  beef or lamb   rare 20, medium 25, well done 30 minutes   at 180 °C (350 °F)
  pork           30 minutes                                 at 180 °C (350 °F)
  chicken        20 minutes                                 at 190 °C (375 °F)

  rest  ≈  a quarter of the cooking time, 10 to 30 minutes

Step-by-Step Example

A 2 kg joint of beef, medium.

  Weight:      2,000 g ÷ 500           =  4
  Time:        4 × 25 + 25             =  125 min  (2 h 5 min)
  Take out at: 58–60 °C (136–140 °F)
  Rest:        125 ÷ 4 ≈ 31            →  30 min

A 1.5 kg chicken.

  Time:        3 × 20 + 20             =  80 min  (1 h 20 min) at 190 °C
  Done at:     74 °C (165 °F) in the thigh

Internal Temperatures

The temperature of a large joint keeps rising by a few degrees while it rests, known as carryover cooking, so it is taken out just before the target. Food safety agencies recommend at least 63 °C (145 °F) followed by a rest for whole cuts of beef, lamb and pork; rare beef is a personal choice that many people make with whole joints, because bacteria live on the surface, which is well seared. Minced meat and poultry must always be cooked through.

Why Use a Thermometer

The time rule assumes an average joint in an accurate oven. A long, thin joint cooks faster than a round, thick one of the same weight; a joint on the bone cooks a little differently from a boned and rolled one; and many ovens run hotter or cooler than their dial. An instant-read or probe thermometer pushed into the thickest part of the meat, away from the bone, removes the guesswork. Start checking about 20 minutes before the calculated time.

Getting a Good Crust

Many cooks start a roast in a hot oven, around 220 °C (425 °F), for 15 to 20 minutes to brown the outside, then turn it down for the rest of the time. If you do this, reduce the total time slightly. Patting the meat dry, seasoning it well with salt an hour or more ahead, and letting it come out of the fridge 30 to 60 minutes before cooking all help it brown evenly. For crackling on pork, score the skin, rub it with salt and keep it dry.

Fan and Convection Ovens

A fan oven cooks more quickly because moving air transfers heat faster. Set it about 20 °C lower than a conventional oven — 160 °C instead of 180 °C — and check the internal temperature 10 to 15 minutes earlier than the time suggests.

Resting the Meat

Resting is not optional. Straight out of the oven, the juices are concentrated in the centre and run out as soon as the meat is cut. After a rest, loosely covered with foil, they spread back through the joint, and the meat carves neatly and stays moist. A quarter of the cooking time is a good guide, from about 10 minutes for a small joint to 30 minutes for a large one. The rest is also the time to make the gravy from the pan juices.

Choosing a Joint

For beef, rib and sirloin are the classic tender roasting joints; topside and silverside are leaner and best served pink and sliced thinly, because they dry out when well done. Leg and shoulder of lamb both roast well, with shoulder richer and more forgiving. Pork loin gives neat slices and crackling, while pork shoulder suits slow roasting. Allow about 200 to 250 grams of boneless raw joint per person, or more for a joint on the bone. A 2 kilogram boneless beef joint feeds around eight people with leftovers for sandwiches.

Slow Roasting

Tougher cuts such as pork shoulder, lamb shoulder and beef brisket do not suit the minutes-per-500-grams rule. They are roasted low and slow, around 150 °C, for several hours until the connective tissue melts and the meat pulls apart easily.

Understanding Your Result

Cooking time is the total time in the oven and the oven temperature.

Joint confirms the weight, meat and doneness.

Rule used shows the minutes per 500 g applied.

Internal temperature gives the temperature to take the meat out at.

Resting gives the resting time before carving.

Fan oven gives the lower temperature for a fan or convection oven.

When Should You Use This Calculator?

Cooking a Sunday roast or a holiday dinner.

Timing a meal so everything is ready together.

Cooking an unfamiliar cut or meat.

Converting a pound-based recipe to kilograms.

Adjusting for a fan oven.

Common Mistakes

Cooking straight from the fridge, which makes the time unreliable.

Not using a thermometer.

Skipping the rest and losing the juices.

Forgetting carryover cooking, so rare becomes medium.

Using conventional temperatures in a fan oven.