What this calculator works out
Enter the meat and its weight and this gives a roasting time, the oven setting to use, the core temperature to aim for and how long to rest it afterwards.
Treat the time as a guide and the temperature as the answer. Roasting times assume a shape, a starting temperature and an accurate oven, and none of those holds reliably. A probe thermometer in the thickest part of the meat is the only dependable test.
Food Standards Agency guidance is that food should reach a core temperature of 70°C for two minutes, or an equivalent time and temperature combination. Whole cuts of beef and lamb are the exception, and this page explains exactly where that exception stops.
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Before you calculate
Roasting times assume a particular shape, a particular starting temperature and an oven that is accurate. None of those is reliable. The only dependable check is a probe thermometer in the thickest part of the meat, away from bone. The Food Standards Agency's standard advice is that food should reach a core temperature of 70°C for two minutes, or an equivalent combination.
- Weigh the bird or joint after stuffing, because the stuffing adds both weight and cooking time.
- Take meat out of the fridge 30 to 60 minutes before it goes in, so it is not fridge-cold in the middle.
- Rest the meat afterwards. The temperature continues to rise a few degrees while it rests, and the juices redistribute.
How this calculator works
Time = (minutes per kg × weight in kg) + a fixed additionRoasting time is not simply proportional to weight, because heat travels inwards from the surface. A joint twice as heavy is not twice as thick, so it does not take twice as long. The fixed addition accounts for the time taken to heat the outer layers before the centre starts to rise at all.
The rates used are the conventional British ones for an oven at 180°C conventional, or 160°C fan, or gas 4. Pork and poultry have no doneness choice because both need to be cooked through.
Core temperatures
| Meat | Target core | Notes |
|---|---|---|
| Chicken and turkey | 70°C for 2 min | Many cooks aim for 74°C for certainty. No pink meat, juices run clear |
| Pork | 70°C | Cooked through, no pink |
| Beef and lamb, rare | 52 to 55°C | Whole cuts only, with the outside properly sealed |
| Beef and lamb, medium | 60 to 65°C | Whole cuts only |
| Beef and lamb, well done | 70°C and above | Safe for any cut |
| Minced, rolled or stuffed joints | 70°C for 2 min | No exception. Bacteria are mixed through, not just on the surface |
The rare and medium temperatures apply only to whole cuts of beef or lamb. Anything minced, rolled, stuffed, or pierced with a larding needle has had surface bacteria carried into the middle, and must reach 70°C throughout. The same applies to all poultry and pork regardless of cut.
The FSA also gives equivalent time and temperature combinations: 60°C for 45 minutes, 65°C for 10 minutes, 70°C for 2 minutes, 75°C for 30 seconds, or 80°C for 6 seconds. All achieve the same reduction in harmful bacteria.
Worked example: a 1.8 kg chicken
- Rate for whole chicken: 45 minutes per kg, plus 20 minutes
- Time: (45 × 1.8) + 20 = 81 + 20 = 101 minutes, or about 1 hour 40 minutes
- Oven: 180°C conventional, 160°C fan, gas 4
- Rest: 15 to 20 minutes before carving
Start checking with a probe about fifteen minutes before the calculated time. An accurate oven and a well-shaped bird will often be ready early, and a long flat joint cooks faster than a compact one of the same weight.
Common mistakes
- Trusting time over temperature. The calculated time gets you close. The probe tells you when it is done.
- Probing near a bone. Bone conducts heat and reads higher than the surrounding meat.
- Weighing before stuffing. Stuffing adds weight and slows heat reaching the centre.
- Roasting straight from the fridge. A cold centre adds time unpredictably.
- Not resting. Carving immediately loses juice and the temperature has not finished rising.
- Applying rare temperatures to rolled or stuffed joints. The safety logic does not survive rolling.
Frequently asked questions
How do I know when a chicken is properly cooked?
A probe in the thickest part of the thigh, kept away from the bone, reading at least 70°C and held there for two minutes. Many cooks aim for 74°C for margin. Supporting signs are meat that is not pink and juices that run clear, but colour on its own is not reliable — poultry can look done before it is.
Why can beef be eaten rare but not chicken?
On a whole cut of beef, bacteria are on the surface, which reaches a high temperature quickly. The interior was effectively sterile before cutting. Poultry carries bacteria such as campylobacter and salmonella throughout, and mincing or rolling any meat carries surface bacteria inside. That is why whole cuts of beef and lamb can be served rare while poultry, pork, mince and rolled joints cannot.
Does the calculator account for a fan oven?
The times assume 180°C conventional, which is 160°C in a fan oven. Set the fan oven to 160°C and use the same times, then check early with a probe. Setting a fan oven to 180°C will brown the outside well before the middle is ready.
How long should meat rest?
Roughly 10 to 15 minutes for a small joint or chicken, 20 to 30 for a large joint, and 30 to 45 for a big turkey. Cover it loosely with foil. The core temperature continues to climb by a few degrees during resting, which is worth allowing for if you are aiming at a precise doneness.
What if my joint is boned and rolled?
Treat it as needing 70°C throughout, whatever the cut. Rolling puts what was the outer surface, and any bacteria on it, into the centre. Rolled joints also cook more slowly than a flat piece of the same weight because they are thicker.
Can I cook a turkey overnight at a low temperature?
It is done, but it needs care and a reliable probe, because the meat spends a long time passing through the temperature range where bacteria multiply. The FSA identifies 5 to 63°C as the danger zone. If you are not confident about your oven's accuracy at low settings, conventional roasting is the safer choice.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
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References
These organisations publish the guidance and figures behind this page.
- Food Standards Agency — cooking safely — the source of the 70°C for two minutes core temperature guidance and its equivalents
- Food Standards Agency — UK food safety guidance for home cooks and businesses
- NHS — eat well — portion guidance and healthy eating advice
Cooking guidance is general information, not a substitute for a thermometer. If in doubt, cook for longer and check the core temperature.