Roasting Time Calculator

The rate varies by meat and doneness (Waitrose / BBC Good Food, at 180°C conventional / 160°C fan / Gas 4): Beef rare is 20 minutes per 500g plus 20 minutes, medium is 25 minutes per 500g plus 25 minutes, well done is 30 minutes per 500g plus 30 minutes. Lamb is the same — medium 25 minutes per 500g plus 25, well done 30 per 500g plus 30. Pork is cooked thoroughly at 30 minutes per 500g plus 30 minutes. Chicken is roughly 20 minutes per 500g plus 20 minutes (190°C / Gas 5). Turkey is 20 minutes per kg plus 70 minutes under 4kg, or plus 90 minutes from 4kg upwards (190°C / 170°C fan / Gas 5). These are starting points — always confirm the joint is done with a meat thermometer.

Fan ovens circulate hot air and run about 20 degrees C cooler than conventional ovens for the same result. This calculator shows both, plus the Gas mark. The roasting times here are calibrated to the conventional setting shown (for example 180°C conventional, 160°C fan, Gas 4 for beef, lamb and pork) — pick the line that matches your oven and the time stays the same. If you only have a fan oven, use the lower fan figure.

Resting is essential. When meat cooks, the heat forces juices towards the centre. Resting allows these juices to redistribute throughout the joint, resulting in moister, more tender meat. A general rule is 1 minute per 100g, with a minimum of 10 minutes and maximum of 30 minutes. Tent the meat loosely with foil during resting — do not wrap tightly or the crust will go soggy.

A digital meat thermometer is the most reliable method — insert it into the thickest part, away from any bone. Whole beef and lamb joints (intact muscle, seared on the outside) may be served pink: beef rare 52°C, medium-rare 57°C, medium 63°C, well done 71°C; lamb medium 63°C, well done 71°C. Pork should reach 75°C at the core, or 70°C held for at least 2 minutes (FSA equivalence). Chicken and turkey must reach 75°C in the thickest part of the thigh. For pork and poultry the juices should run clear with no pink meat. Minced, rolled or reformed joints have no safe rare option — cook them right through to 75°C.

Taking meat out of the fridge 30-60 minutes before cooking allows it to come closer to room temperature, which helps it cook more evenly. A large joint straight from the fridge will have a cold centre that takes longer to reach temperature, potentially overcooking the outside. For food safety, do not leave meat out for more than 2 hours.