How do I calculate roasting time per kilogram?

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. These are starting points — always confirm the joint is done with a meat thermometer.

Should I use fan or conventional oven temperatures?

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.

How important is resting meat after roasting?

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.

How do I check if meat is cooked properly?

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.

Should I bring meat to room temperature before roasting?

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.

Roasting Time Calculator — Free Online Tool

How We Calculate This

This calculator uses established UK roasting time guidance (Waitrose, BBC Good Food) based on the weight of your joint and the type of meat. Each meat has a time per 500g plus an additional fixed time. Doneness affects the per-500g rate for beef and lamb; pork, chicken and turkey are always taken to well done for food safety.

Resting time is calculated at 1 minute per 100g of meat, with a minimum of 10 minutes and maximum of 30 minutes. Temperatures are given as the conventional oven setting with the fan and Gas-mark equivalents alongside — the times match the conventional figure shown.

Times are a guide to reaching a safe, well-rested joint, not a guarantee. Always check the core with a meat thermometer: pork, chicken and turkey to 75°C (or pork 70°C held for 2 minutes); whole beef and lamb joints to your chosen doneness (rare 52°C up to well done 71°C). Minced or rolled joints must be cooked right through to 75°C.

Frequently Asked Questions

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Last updated: June 2026

All calculations are based on standard ratios and conversions. Results may vary with specific ingredients, equipment, and conditions.