Cooking Time Calculator
Twice the weight is nowhere near twice the time.
Work out Cooking Time. Twice the weight is nowhere near twice the time. Names the misconception directly.
Time in the oven
1h 40m
Ready 2h 00m from now, including 20 minutes resting
Cooking time does not scale with weight. Heat travels inward from the surface, and a joint twice the mass is not twice the thickness — which is why the fixed allowance exists and why a doubled weight takes well under double the time. The only reliable finish test is a probe thermometer: carryover cooking continues after the joint leaves the oven, so pulling it a few degrees short is what stops it overshooting.
How the Cooking Time Calculator works
Roasting time from a rate per kilogram plus a fixed allowance, with the resting time and the temperature to pull the joint at. The fixed allowance is what stops the estimate scaling linearly, which is the whole point.
Also known as: how long to roast a joint · meat cooking time per kilogram · roasting time by weight · how long does beef take in the oven
Why time does not scale with weight
Heat enters a joint through its surface and travels inward by conduction, so what governs cooking time is thickness rather than mass. A joint twice the weight is nowhere near twice as thick — for a roughly spherical shape it is only about 26% thicker.
That is why the calculation is a rate per kilogram plus a fixed allowance rather than a simple multiplication. The fixed part represents the time to get heat moving at all, and it stops the estimate scaling linearly in a way that would badly overcook a large joint.
Shape matters as much as weight for the same reason. A long thin joint cooks far faster than a compact one of identical mass, which is why any time-per-kilogram figure is an estimate and why a probe thermometer is the only reliable finish test.
Carryover cooking and the temperature to pull at
A joint keeps cooking after it leaves the oven. Heat stored in the outer layers continues moving inward, and the internal temperature typically rises another 3 to 7 °C depending on size — more for a large roast, less for a small one.
Which means pulling the joint at the target temperature overshoots it. Pulling a few degrees short and letting carryover finish the job is what lands it where intended, and it is the difference between medium-rare and medium on a beef joint.
Resting serves a second purpose beyond temperature. The muscle fibres relax and the juices redistribute, so less runs out on carving. Twenty minutes suits a medium joint and a large bird wants thirty to forty-five, during which it stays far hotter than people expect.
What searing does and does not do
Searing browns the surface through the Maillard reaction, which generates several hundred flavour compounds that do not exist in the raw meat. That is a real and substantial contribution and it is the reason to do it.
It does not seal in juices. That claim originated in the nineteenth century, was disproved by straightforward experiment decades ago, and persists in cookery writing anyway. Seared meat loses about as much moisture as unseared meat, sometimes slightly more.
The related practical point is that a cut needs the cooking method its structure calls for. Collagen-rich cuts — shoulder, shin, brisket — need long low heat to convert collagen to gelatine. Lean cuts need the opposite, and treating one as the other is the most common reason a roast comes out tough.
Where to go next
The Cooking Time question rarely arrives on its own. These are the ones that usually come with it:
- Turkey Cooking Time Calculator — The breast and the thigh finish at different times.
- Oven Temperature Converter — Your oven is probably not the temperature it claims.
- Serving Size Calculator — Meat shrinks, rice swells — buy by the raw weight.
- Ring Size Calculator — Finger measurement to US, UK, EU and Japanese sizes.
Frequently asked questions
How long do I cook a joint per kilogram?
It depends on the meat and the finish you want, which is why the rate is an input. The structure matters more: time is a rate per kilogram plus a fixed allowance, not a simple multiplication.
Why isn't twice the weight twice the time?
Because heat travels inward from the surface, and a joint twice the mass is nowhere near twice as thick. Doubling the time overcooks the outside long before the centre is ready.
What is carryover cooking?
The internal temperature keeps rising after the joint leaves the oven, typically by 3 to 7 °C depending on size. Pulling it a few degrees short is what stops it overshooting.
Why does meat need to rest?
Resting lets the temperature even out and the juices redistribute, so less runs out when it is carved. Twenty minutes for a medium joint, longer for anything large.
Is a meat thermometer necessary?
It is the only reliable finish test. Time per kilogram is an estimate built on assumptions about starting temperature, oven accuracy and joint shape, all of which vary.
Should meat come to room temperature first?
Taking the chill off helps it cook more evenly, and thirty to sixty minutes out of the fridge is common practice. Longer than that on a large joint raises food safety questions.
What internal temperatures matter?
They differ by meat and by food safety authority, and poultry is the one with the least room for interpretation. Use the published figure for your country rather than a remembered number.
Does the shape of a joint matter more than its weight?
Yes. Heat penetrates by thickness, so a long thin joint cooks far faster than a compact one of the same weight. That is why time per kilogram is only ever an estimate.
Should I cover the joint with foil?
Covering slows browning and speeds the interior. A common approach is to roast uncovered and tent with foil once the colour is right, which prevents further browning while the centre catches up.
What does searing actually do?
It browns the surface through the Maillard reaction, which creates flavour. It does not seal in juices — that claim was disproved decades ago and persists anyway.
Why does my roast come out tough?
Either overcooked, or a cut that needed slow cooking treated as a fast roast. Collagen-rich cuts need long low heat to break down; lean cuts need the opposite.
Can I roast from frozen?
Not safely for a large joint — the outside overcooks long before the centre is safe. Thaw fully in the refrigerator, allowing roughly a day per two kilograms.
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