Lamb Joint Calculator

For lamb at 160°C fan (180°C conventional, Gas 4): Medium is 25 minutes per 500g plus 25 minutes. Well done is 30 minutes per 500g plus 30 minutes. Pink (rare) lamb is 20 minutes per 500g plus 20 minutes. A 1.5kg leg of lamb at medium takes about (1500/500 x 25) + 25 = 100 minutes. Use a meat thermometer to confirm doneness.

The leg is the most popular roasting cut — it has good flavour and feeds a crowd. Shoulder is fattier and more flavourful, excellent for slow roasting until it falls apart. Rack of lamb (French-trimmed) is elegant but smaller and cooks quickly. Half-leg or mini roast joints are perfect for smaller households. Bone-in joints generally have more flavour than boneless.

A whole lamb joint (intact muscle such as a leg, shoulder or rack) is traditionally served pink in the UK and is safe this way, unlike minced lamb, pork or chicken which must reach 75°C. The Food Standards Agency advises a minimum core of 63°C for whole lamb joints. Medium (63°C internal) gives juicy, flavourful meat with a pink centre; well done (71°C) is also popular. Rare lamb (52°C) is less common but favoured by some chefs for tender cuts like rack. Always check the centre of the thickest part with a meat thermometer rather than relying on time alone. Minced lamb, burgers and sausages must be cooked right through to 75°C.

Garlic and rosemary are the classic accompaniments to roast lamb. Make small incisions in the meat with a sharp knife and push in slivers of garlic and small sprigs of rosemary before roasting. Anchovies pushed into the incisions also work beautifully — they melt into the meat during cooking and add umami depth without a fishy taste.

Score the fat in a criss-cross pattern, rub with oil and salt, and start the oven at 220°C for the first 20 minutes before reducing to 180°C. The high initial heat renders the fat and crisps the skin. For shoulder, slow-roasting at 160°C for several hours also produces excellent crispy skin as the fat renders gradually over a longer period.