Show the formula and working
This meat roasting time calculator works out how long to roast a joint of beef, lamb or pork, or a whole chicken, from its weight, and counts back from your meal time so you know exactly when it goes into the oven. It is designed for Sunday roasts in the UK and Ireland, uses kilograms, and follows timings published by British meat industry bodies and the Irish food safety agency.
Quick answer: Roast beef for 20 minutes per 450 g plus 20 minutes for rare, 25 plus 25 for medium and 30 plus 30 for well done. Lamb takes 25 plus 25 for medium, pork 30 plus 30, and a whole chicken 20 minutes per 450 g. The meat roasting time calculator applies these to your joint.
What Is a Meat Roasting Time Calculator?
A meat roasting time calculator is a tool that estimates oven time for a joint from its weight and the way you like it cooked. British roasting times are traditionally given per 450 g (1 lb), so the formula is: roasting time = (weight in grams / 450) x minutes per 450 g + extra minutes. The calculator then subtracts the roasting time and your resting time from your meal time to give the moment the joint goes in.
The beef and lamb timings come from the recipes of Simply Beef and Lamb, run by the Agriculture and Horticulture Development Board (AHDB). The pork timing comes from AHDB’s Love Pork roast leg recipe, and the chicken timing from safefood, the food safety body for the island of Ireland. If your label or butcher gives different times, use the Custom times option.
How Do You Use the Meat Roasting Time Calculator?
- Choose Meat and how you like it, for example “Beef, medium” or “Pork”.
- Enter the Joint weight in kilograms, weighed after stuffing if the joint is stuffed.
- If you picked “Custom times”, fill in Custom minutes per 450 g and Custom extra minutes from your label or recipe.
- Set Time you want to eat (24 hour clock), for example 13 for 1pm.
- Choose your Resting time (your choice) in minutes.
- Read the roasting time and oven times, then open “Show the formula and working” to check the sums.
How Long Do You Roast a 1.5 kg Beef Joint?
A 1.5 kg beef joint takes about 1 hour 48 minutes for medium at 180 to 190 C (160 to 170 C fan, gas 4 to 5). Rare takes about 1 hour 27 minutes and well done about 2 hours 10 minutes. The sum for medium is 1,500 g / 450 = 3.33, then 3.33 x 25 minutes plus 25 minutes.
Which Meats Must Be Cooked Through?
Poultry, pork, rolled joints, minced meat and sausages must be cooked all the way through, while whole joints of beef and lamb can be served pink. According to safefood’s guide to checking meat is cooked, bacteria on a whole beef or lamb joint are usually only on the outside surface, so once that is properly cooked the inside can be rare. For meats that must be cooked through, the centre should be steaming hot with no pink meat and clear juices, or reach 75 C on a food thermometer. The Food Standards Agency also accepts equivalent combinations such as 70 C held for 2 minutes.
Why Should You Rest Meat After Roasting?
Rest a roast joint out of the oven, loosely covered with foil, before you carve it; the calculator uses 20 minutes as an editable example. Resting makes the joint easier to carve and gives you time to make gravy and finish the vegetables while the meat stays hot. Whatever time you choose is built into the oven times, so nothing is rushed at the end.
Do Fan Ovens Need a Different Temperature?
Fan ovens are usually set about 20 C lower than conventional ovens, which is why the Food Standards Agency pairs 180 C with 160 C fan and Love Pork gives 180 C or 160 C fan for pork. Keep the roasting time the same and use the matching fan temperature. If you are unsure of your oven’s true temperature, an oven thermometer is a cheap way to check, and a meat thermometer removes most of the guesswork. A long roast also uses a fair amount of energy, which the electricity cost calculator can price for your oven.
| Meat | Timing | Oven (preheated) | 1 kg joint | 2 kg joint |
|---|---|---|---|---|
| Beef, rare | 20 min per 450 g plus 20 min | 180 to 190 C, 160 to 170 C fan, gas 4 to 5 | 1 h 04 min | 1 h 49 min |
| Beef, medium | 25 min per 450 g plus 25 min | 180 to 190 C, 160 to 170 C fan, gas 4 to 5 | 1 h 21 min | 2 h 16 min |
| Beef, well done | 30 min per 450 g plus 30 min | 180 to 190 C, 160 to 170 C fan, gas 4 to 5 | 1 h 37 min | 2 h 43 min |
| Lamb, medium | 25 min per 450 g plus 25 min | 180 to 190 C, gas 4 to 5 | 1 h 21 min | 2 h 16 min |
| Lamb, well done | 30 min per 450 g plus 30 min | 180 to 190 C, gas 4 to 5 | 1 h 37 min | 2 h 43 min |
| Pork | 30 min per 450 g plus 30 min | 180 C, 160 C fan, gas 4 | 1 h 37 min | 2 h 43 min |
| Whole chicken | 20 min per 450 g | 190 C, gas 5 | 44 min | 1 h 29 min |
Lamb timings in the Simply Beef and Lamb recipes are given for conventional and gas ovens; for a fan oven, use about 20 C less. Always confirm a chicken is cooked through in the thickest part of the thigh.
Worked Example: Sunday Roast Beef at 1pm
Example: a 1.5 kg topside of beef is to be served medium, with the meal at 1pm and 20 minutes of resting while the gravy is made. Choose “Beef, medium”, enter 1.5 kg, set the meal time to 13 and leave resting at 20 minutes.
- Weight in 450 g units: 1,500 g / 450 = 3.33
- Roasting time: 3.33 x 25 min + 25 min = 108 min (1 h 48 min)
- Into the oven: 13:00 minus 1 h 48 min roasting and 20 min resting = 10:52
- Out of the oven: 12:40, then rest until 13:00
Preheat the oven to 180 C at about 10:30 and put the beef in at 10:52. For more planning tools around the house, browse our home calculators.
Meat Roasting Time Calculator FAQs
How long do you roast beef per kg?
Using 450 g timings, medium beef works out at about 55.6 minutes per kg plus 25 minutes, rare at about 44.4 minutes per kg plus 20 minutes, and well done at about 66.7 minutes per kg plus 30 minutes, at 180 to 190 C or 160 to 170 C fan.
How long does a 2 kg leg of lamb take?
A 2 kg leg of lamb takes about 2 hours 16 minutes for medium (25 minutes per 450 g plus 25 minutes) or 2 hours 43 minutes for well done (30 minutes per 450 g plus 30 minutes) at 180 to 190 C, gas 4 to 5. Add resting time before carving.
How long does a pork joint take?
Allow 30 minutes per 450 g plus 30 minutes at 180 C, 160 C fan or gas 4, following Love Pork’s roast leg timing. A 2 kg joint takes about 2 hours 43 minutes. Pork must be cooked through, so check the centre is steaming hot or reaches 75 C.
How long does a whole chicken take to roast?
safefood’s roast chicken recipe allows 20 minutes for every 450 g at 190 C, gas 5, so a 1.8 kg chicken takes about 1 hour 20 minutes. Check the thickest part of the thigh is steaming hot, with no pink meat and clear juices, or 75 C on a thermometer.
Do I weigh the joint before or after stuffing?
Weigh the joint after stuffing, because the stuffing has to heat through as well and adds to the time. Stuffed and rolled joints must also be cooked all the way through, even if they are beef or lamb, since the outside surface has been rolled into the middle.
Can I use these times for a boneless joint?
Yes, as a starting point, but shape matters as much as weight. A long thin joint cooks faster than a short thick one of the same weight. Start checking 15 to 20 minutes early with a food thermometer, and use Custom times if the label gives its own timing.
Checked October 2026. Sources: Simply Beef and Lamb (AHDB): Roast beef timings, Simply Beef and Lamb (AHDB): Roast leg of lamb timings, Love Pork (AHDB): Roast leg of pork, safefood: Roast chicken, safefood: How to check your meat is cooked, Food Standards Agency: Christmas food hygiene.