What is the formula for roasting beef?

For beef at 160°C fan (180°C conventional / gas mark 4): 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. So a 1.5kg joint at medium takes about (1500/500 x 25) + 25 = 100 minutes. These times follow the Waitrose roast-beef guide. Always verify with a meat thermometer for the most accurate results — for whole beef joints the surface should be fully seared, and reformed or minced beef must reach 75°C.

What are the internal temperatures for beef doneness?

The target internal temperatures for a whole beef joint (measured with a probe thermometer in the thickest part, away from bone) are: Rare 52°C, Medium-rare 56°C, Medium 60°C, Medium-well 65°C, and Well done 71°C. Rare and medium are safe for an intact muscle joint because bacteria sit only on the surface, which is fully cooked when seared — but minced or reformed beef must always reach 75°C. Remember the temperature will continue to rise by 3-5°C during resting (carry-over cooking), so remove the joint about 3-5°C below your target.

Which beef cuts are best for roasting?

The best cuts for roasting are topside, silverside, sirloin, rib of beef, and rump. Rib of beef (bone-in) is considered the finest roasting joint with excellent flavour and marbling. Topside and silverside are leaner and more affordable but can dry out if overcooked — medium-rare to medium is ideal for these cuts. Sirloin and rump have good fat content for a flavourful roast.

Should I sear beef before roasting?

Searing is optional but recommended for the best flavour, and for whole joints it also helps ensure the surface bacteria are killed. Heat a heavy pan to smoking hot and sear the joint on all sides for 1-2 minutes each until well browned. This creates a Maillard reaction crust that adds deep flavour. Alternatively, start the oven at 220°C (200°C fan) for the first 20 minutes, then reduce to 180°C conventional / 160°C fan for the remaining time given by this calculator. Both methods achieve a similar result.

How many people does a beef joint serve?

Allow approximately 300g of raw bone-in beef per person, or 200-250g for boneless joints. A 1.5kg boneless joint serves about 5-6 people. For a bone-in rib of beef, allow more weight per person as the bone adds weight without adding meat. If you want leftovers for sandwiches, add an extra 500g to your total.

Beef Joint Calculator — Free Online Tool

How We Calculate This

This calculator uses the standard UK beef roasting formula (Waitrose roast-beef guide) at 160°C fan / 180°C conventional / gas mark 4. The time per 500g increases with doneness: 20 minutes for rare, 25 for medium, and 30 for well done, each with a matching additional base time. Medium-rare is an interpolated estimate (22 minutes per 500g plus 22) sitting between the published rare and medium bands.

Resting time is calculated at 1 minute per 100g, with a minimum of 15 minutes and maximum of 30 minutes. Internal temperatures account for approximately 3-5°C of carry-over cooking during rest.

Food safety: a whole, intact beef joint can be served rare or medium because harmful bacteria sit only on the surface, which is destroyed when the outside is fully seared. Minced, rolled or reformed beef has no safe rare option and must reach a 75°C core (or 70°C held for 2 minutes). Always confirm doneness with a meat thermometer rather than relying on time alone.

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Last updated: February 2026

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