Roast Cooking Time Calculator

Roasting time by weight from USDA FSIS’s own charts, reproduced in full because they are US Government work — and re-read as the scaling law the physics asks for, because FSIS’s own turkey timetable implies 17.3 minutes per pound at 10 lb and 13.0 at 22 lb. A joint twice the weight does not take twice as long. The thermometer, not the clock, decides when it is done.

Last updated 24 Sep 2026

Roasting time by weight and cut

Cut + weight → time to allow

Which cut?Every row is USDA FSIS’s own published chart, with the oven temperature and the weight range it was published for. Change the oven and the row no longer applies.

WeightThe raw weight of the joint or bird, in the unit beside it.

A plot, not a circuit, and normalised so that it is the same picture for every cut on this page: weight divided by the middle of the chart's own weight range along the bottom, time divided by the time at that weight up the side. The straight line is what a minutes-per-pound rate says — double the weight, double the time. The curve is what conduction says: time scales as the square of a length and therefore as mass to the two thirds, so double the weight is 1.587 times the time. They cross at the middle of the chart's range by construction, and they part in both directions away from it. The cross marks the per-pound answer for your joint and the diamond the scaling answer; this page always reports the longer of the two, which is the curve below the crossing and the line above it.

138minExample

a 2.5 kg bone-in beef rib roast at 325 °F, on FSIS’s chart

A published rate, and the scaling the rate hides

time = (minutes per pound) × weight · time = t₀ × (W / W₀)^(2/3) · time to allow = the LONGER of the two · British form: time = r × W / 450 g + 20 min

minutes per pound: what FSIS publishes, and it belongs to one cut at one oven temperature over one weight range. Outside any of those three it is not a figure about anything
W₀: the middle of the chart’s own weight range. The two models are made to agree there, so away from it you can see how far apart they get
2/3: heat reaches the centre by conduction, so the time scales as the square of a LENGTH — and length is the cube root of mass at constant shape. Doubling the weight multiplies the time by 2^(2/3) = 1.587, not by 2
the longer of the two: deliberate. Below the chart’s mid-weight a per-pound rate under-predicts, and that is the dangerous direction; above it the rate is the longer figure anyway. The headline is never the shorter of the two models
+ 20 min: the fixed term. British charts have always had one, and a least-squares line through FSIS’s own turkey chart wants 81 minutes of it
internal temperature: the only figure here that decides anything. FSIS: 145 °F (62.8 °C) plus a three-minute rest for whole cuts of beef, pork, lamb and veal; 165 °F (73.9 °C) for all poultry and for stuffing

Worked example

a 2.5 kg bone-in beef rib roast at 325 °F, on FSIS's chart
2.5 kg is 5.512 lb, which is inside the 4 to 6 lb range FSIS published this row for
The chart gives 23 to 25 minutes per pound, so 127 to 138 minutes
Re-read as a scaling law anchored at the middle of the chart's range — 5 lb, where 25 min/lb gives 125 minutes — the same figure is 125 × (5.512/5)^(2/3) = 133 minutes. This joint is above the anchor, so the published rate is the longer of the two and the headline is 138 minutes
On the British convention the same joint is 131 minutes for rare, 159 for medium and 187 for well done — a spread of 56 minutes that has nothing to do with safety and everything to do with how you like it
None of those numbers finishes the job. FSIS's minimum for this cut is 145 °F, 62.8 °C, plus a three-minute rest. Put a probe in the thickest part, away from bone, and start looking at 127 minutes

The USDA FSIS charts this page computes from

Reproduced directly, because these are works of the United States Government and in the public domain. Two things to notice. First, the minutes-per-pound figure is tied to an oven temperature and a weight range: a rib roast at 23–25 min/lb is a rib roast at 325 °F between 4 and 6 lb, and nothing else. Second, two cuts are published as a total time rather than a rate, which is a tacit admission that the relation is not proportional. The minimum internal temperature column is the only column on this page that is a requirement rather than an estimate — everything else is guidance and the thermometer overrules it.
Cut	Oven (°F)	Weight range (lb)	Minutes per pound	Total minutes	Minimum internal (°F)	Rest (min)	Which chart
Beef rib roast, bone-in	325	4–6	23–25	—	145	3	FoodSafety.gov chart
Beef rib roast, boneless	325	4–6	28–33	—	145	3	FoodSafety.gov chart
Beef round or rump roast	325	2.5–4	30–35	—	145	3	FoodSafety.gov chart
Beef tenderloin, whole	425	4–6	—	45–60	145	3	FoodSafety.gov chart
Lamb leg, bone-in	325	5–9	20–26	—	145	3	FSIS holiday chart
Lamb leg, boneless, rolled	325	4–7	25–30	—	145	3	FoodSafety.gov chart
Lamb shoulder roast	325	3–4	30–35	—	145	3	FoodSafety.gov chart
Pork loin roast, bone-in or boneless	350	2–5	20	—	145	3	FoodSafety.gov chart
Pork Boston butt	350	3–6	45	—	145	3	FoodSafety.gov chart
Pork tenderloin	437	0.5–1.5	—	20–27	145	3	FoodSafety.gov chart
Veal rib roast	325	4–5	25–27	—	145	3	FoodSafety.gov chart
Veal loin	325	3–4	34–36	—	145	3	FoodSafety.gov chart
Turkey, whole, unstuffed	325	8–24	see the turkey table below	—	165	—	FSIS Let’s Talk Turkey
Turkey, whole, stuffed	325	8–24	see the turkey table below	—	165	—	FSIS Let’s Talk Turkey
Capon, whole	375	4–8	20–30	—	165	—	FSIS holiday chart
Goose, domestic or wild	325	6–12	20–25	—	165	—	FSIS holiday chart
Duck, domestic	375	3–6	20	—	165	—	FSIS holiday chart

FSIS’s turkey timetable at 325 °F, and the rate hidden inside it

The sixth column is the finding. FSIS’s own chart implies 17.25 minutes per pound at 10 lb and only 12.95 at 22 lb — a quarter less. A roasting time is NOT proportional to weight, and this is a US Government chart saying so. Fit a power law to those five midpoints and the exponent comes out at 0.649; fit a straight line and you get 81 minutes plus 9.5 per pound, which is the “per pound plus a fixed time” form British charts have always used. A single minutes-per-pound rate through the origin cannot fit these five points to better than twenty minutes, however you choose it. The last column is FSIS’s stuffing allowance as their own two charts imply it, and it brackets the 15 to 30 minutes their holiday guidance states. Stuffing must itself reach 165 °F.
Weight (lb)	Unstuffed (hours)	Stuffed (hours)	Band midpoint (lb)	Midpoint time (min)	Implied minutes per pound	Stuffed adds (min)
8 to 12	2.75 to 3	3 to 3.5	10.0	173	17.25	23
12 to 14	3 to 3.75	3.5 to 4	13.0	203	15.58	23
14 to 18	3.75 to 4.25	4 to 4.25	16.0	240	15.00	8
18 to 20	4.25 to 4.5	4.25 to 4.75	19.0	263	13.82	8
20 to 24	4.5 to 5	4.75 to 5.25	22.0	285	12.95	15

Where the published charts contradict each other, and what this page does about it

Four rows where two charts from the same agency do not agree. Three are differences of specification and one, the lamb row, is a factor of two on a cut where being short is a food-safety matter rather than a texture one. This page does not average them and does not silently pick the shorter. Where a published time could land meat under a legal minimum it is left out, and the reason is printed here rather than buried.
Row	One chart says	The other says	This page
Beef rib roast, boneless, about 4 lb at 325 °F	28–33 min/lb (FoodSafety.gov)	39–43 min/lb (FSIS holiday chart)	Uses the lower, 28–33, and reports the disagreement. The two midpoints differ by a factor of 1.34, which on a 4 lb roast is about 42 minutes.
Lamb leg, bone-in, 7–9 lb at 325 °F	10–15 min/lb (FoodSafety.gov)	20–26 min/lb for the whole 5–9 lb range (FSIS holiday chart)	REFUSES the 10–15 row and uses 20–26. At 10 min/lb an 8 lb bone-in leg would come out of the oven after 80 minutes, against 160 on FSIS’s own other chart. That is not a rounding disagreement and it is not a row worth reproducing.
Beef rib roast, bone-in	23–25 min/lb at 4–6 lb (FoodSafety.gov)	23–30 min/lb at 4–8 lb (FSIS holiday chart)	Uses 23–25 over 4–6 lb, the narrower and better-specified row.
Pork loin roast	20 min/lb at 350 °F (FoodSafety.gov)	20–25 min/lb at 325 °F (FSIS holiday chart)	Uses the 350 °F row, and says so in the results — a rate belongs to an oven temperature.

The British convention on the same 2.5 kg joint

British roasting guidance has always been affine — so many minutes per 450 or 500 grams PLUS a fixed twenty — which is the shape a least-squares line through FSIS’s own turkey chart also takes, and for the same physical reason: a small joint needs proportionally longer than a large one. The rates and the centre temperatures here are Reed’s Butchers’ own published figures. Two warnings. Those centre temperatures are a butcher’s doneness preferences, not a food-safety authority’s minimums: the UK Food Standards Agency’s own rule is 70 °C for two minutes or an equivalent combination, and FSIS’s is 145 °F with a three-minute rest. And doneness is not this page’s subject at all — the meat cooking temperature converter owns every band and every minimum, and it is the page to trust over this table.
Doneness the butcher names	The rule	Minutes	Implied min/lb	Centre temperature the butcher gives (°C)
Rare	20 min per 450 g plus 20	131	23.79	50–52
Medium	25 min per 450 g plus 20	159	28.83	60
Well done	30 min per 450 g plus 20	187	33.87	70

The UK’s rule is a time AND a temperature, not minutes per kilo

The Food Standards Agency publishes equivalences rather than roasting times, and this is the honest way to think about any of it: what kills pathogens is time spent at temperature, and the same lethality can be bought hot and fast or cool and slow. All five of these pairs lie on one thermal-death-time line — computing the implied z value row by row gives 7.15 to 8.30 °C, averaging 7.57 — which is within half a degree of the classic Salmonella figure of 7.5 °C. It also shows that the two authorities are not two spellings of one rule: FSIS’s three minutes at 145 °F is worth about twenty seconds at 70 °C on this z, where the FSA asks for two minutes. FSIS’s rule is for whole cuts, where contamination is on the surface; the FSA’s is for the centre of anything where it may not be.
Core temperature (°C)	… in °F	Hold for	Seconds
60	140	45 min	2,700
65	149	10 min	600
70	158	2 min	120
75	167	30 s	30
80	176	6 s	6

A published rate, the scaling it hides, and one row refused

USDA FSIS publishes roasting charts, they are works of the United States Government, and they are reproduced on this page in full. That is the spine of this calculator: a cut, an oven temperature, a weight range and a rate in minutes per pound, with two cuts published as a total time instead and the turkey published as weight bands. Every row also carries the minimum internal temperature FSIS require, because that is the only number in the whole exercise that is a requirement rather than an estimate.

The charts are not proportional to weight, and FSIS’s own turkey timetable is the clearest demonstration of it in print. Take the midpoint of each of its five weight bands and divide the time by the weight, and the implied rate falls from 17.25 minutes per pound at 10 lb to 12.95 at 22 lb. A quarter less, monotonically, across one published table. No single minutes-per-pound figure fits those five points to better than twenty minutes however you choose it. Fit a power law instead and the exponent is 0.649; fit a straight line and you get 81 minutes plus 9.5 per pound.

Why 0.649? Because heat travels by conduction, and conduction scales with a length rather than with a mass. The time for the centre of a body to reach a given temperature goes as the square of its characteristic thickness — double the thickness and the time quadruples, which you can confirm by solving the heat equation numerically and which this page’s proof does. At constant shape and density, thickness goes as the cube root of mass, so time goes as mass to the two thirds: 1.587 times as long for twice the weight, not twice as long. FSIS’s fitted 0.649 is within three per cent of that two thirds, which is a remarkable thing to find in a consumer chart. Shape matters as much as the scaling does. What actually sets the time is the distance from the surface to the coldest point, so a rolled and tied joint takes longer than a flat one of the same weight, and a boned leg longer than the same leg on the bone. That is visible in FSIS’s own rows: boneless rib roast at 28–33 min/lb against 23–25 bone-in.

So this page runs both models and always shows the longer. The published rate and the two-thirds scaling are made to agree at the middle of each chart’s own weight range, which is the weight the rate was really fitted at. Above that weight the rate is the longer figure; below it the scaling law is, because a per-pound rate under-predicts small joints — and under-predicting is the direction that matters when the consequence is raw meat. The headline is therefore never the shorter of the two. The lower bound of the chart’s own range is printed separately, labelled as where to start checking rather than where to stop cooking.

Two authorities, two shapes of rule, and they are not equivalent. The American rule is a target temperature: 145 °F with a three-minute rest for whole cuts, 165 °F for poultry. The British one is a time AND a temperature — the Food Standards Agency publishes 70 °C for two minutes, 75 °C for thirty seconds, 80 °C for six seconds and so on. Those five FSA pairs all lie on one thermal-death-time line with a z value of about 7.6 °C, within half a degree of the classic Salmonella figure, which is a satisfying thing to be able to check. It also shows the two rules are genuinely different in strength: three minutes at 145 °F is worth about twenty seconds at 70 °C on that line, where the FSA asks for two minutes. Both are defensible — FSIS’s rule is aimed at whole cuts, where contamination is on the surface, and the FSA’s at anything where it may not be — but they are not two spellings of one requirement. British roasting guidance in the kitchen is different again: so many minutes per 450 g plus a fixed twenty, at a rate chosen for how you like it, and this page prints all three of those rates alongside the FSIS answer.

Everything about doneness belongs to another page, and one published row is refused outright. This calculator computes time. It quotes the FSIS minimum for the cut you chose and stops there; the meat cooking temperature converter owns the doneness bands, the legal minimums and the carryover rise during resting, and it is the page to trust over any time on this one. The refusal is FoodSafety.gov’s 7-to-9-pound bone-in lamb leg at 10 to 15 minutes per pound, which is half the rate of its own lighter row and less than half what FSIS’s holiday chart gives for the same cut. An 8 lb leg on that row leaves the oven after 80 minutes. It is not offered here. For the oven settings themselves see the oven temperature converter, for an air fryer the air fryer conversion calculator, and for seasoning the joint before it goes in, the brine calculator.

Frequently asked questions

Does a joint twice the weight take twice as long?

No, and FSIS’s own turkey chart proves it. Heat reaches the centre by conduction, so the time scales with the square of a length rather than with mass — and length goes as the cube root of mass at constant shape, which leaves time proportional to mass to the two thirds. Doubling the weight therefore multiplies the time by about 1.59, not by 2. You can read that straight off the published chart: FSIS’s timetable implies 17.3 minutes per pound for a 10 lb bird and 13.0 for a 22 lb one. Fit a power law to their five weight bands and the exponent comes out at 0.65.

Then why do charts print minutes per pound at all?

Because over a narrow weight range it is close enough and it is easy to remember. A per-pound rate is a tangent to the real curve, and it is accurate at one weight — the middle of the range it was published for. Away from that weight it drifts, and at small weights it drifts the dangerous way, predicting a shorter time than the physics wants. That is why this page shows both models, makes them agree at the middle of the chart’s own range, and always headlines the longer of the two. It is also why British charts have a fixed twenty minutes on the end: an affine rule tracks a two-thirds power law far better than a proportional one.

Is the time or the thermometer right?

The thermometer, always, and it is not close. A time estimate knows nothing about your oven’s calibration, how cold the joint was when it went in, whether it was rolled or flat, or how much bone is in it. USDA FSIS require 145 °F (62.8 °C) with a three-minute rest for whole cuts of beef, pork, lamb and veal, and 165 °F (73.9 °C) for all poultry, measured in the thickest part away from bone. Use the clock to decide when to start checking and the probe to decide when to stop. Every minimum, every doneness band and the carryover rise during resting are on the meat cooking temperature converter.

Does shape matter as much as weight?

Yes, and no weight-based chart can see it. What sets the time is the distance from the surface to the coldest point, so a rolled and tied joint and a flat open one of the same weight are different problems — the rolled one is thicker and takes longer. A boned and rolled leg is slower than the same leg on the bone for the same reason, which is why FSIS publish boneless rib roast at 28–33 min/lb against 23–25 bone-in. Bone also conducts, which helps a little. If a joint is unusually long and thin, or unusually compact, expect the chart to be wrong in the obvious direction and trust the probe.

What about a stuffed bird?

It is a separate case with its own published guidance and its own minimum, and this page carries both. FSIS publish a complete stuffed-turkey timetable — select it as a cut above — and their holiday guidance adds 15 to 30 minutes for other stuffed poultry. The stuffing must itself reach 165 °F (73.9 °C), measured in the middle of the cavity, and it is usually the last thing in the bird to get there. FSIS’s own two turkey charts imply a stuffing allowance of 8 to 23 minutes across the weight range, which brackets the 15 to 30 they state.

Why is there no 7 to 9 lb bone-in lamb leg on this page?

Because two US Government charts disagree about it by a factor of two and the shorter figure is not safe to publish. FoodSafety.gov prints 10 to 15 minutes per pound for a 7–9 lb bone-in leg, half the rate of its own 5–7 lb row; FSIS’s holiday chart gives 20 to 26 min/lb for the whole 5–9 lb range. At 10 min/lb an 8 lb leg would leave the oven after 80 minutes against 160 on the other chart. This page uses the 20–26 row for the whole range and leaves the other out, with the reasoning in the table above. Refusing a row is the honest answer when the alternative is a time that could undercook meat.

Why does the oven temperature matter to the rate?

Because a minutes-per-pound figure is not a property of the meat, it is a property of the meat in that oven. FSIS’s rates are published at 325 °F for most cuts, 350 °F for pork loin and 425 °F for the tenderloins, and the results panel prints which one your row assumes. Roast at a different temperature and the rate does not transfer — hotter is faster but also steeper, so the outside overcooks further before the centre arrives. For °C, °F, gas marks and the fan offset, use the oven temperature converter.

Related calculators

References

FoodSafety.gov. Meat and Poultry Roasting Charts. U.S. Department of Agriculture, Food Safety and Inspection Service. A work of the United States Government and in the public domain. The beef, lamb, pork and veal chart is the spine of this page: rib roast bone-in 23–25 min/lb at 325 °F, boneless 28–33, round or rump 30–35, lamb leg boneless 25–30, lamb shoulder 30–35, pork loin 20, Boston butt 45, veal rib 25–27, veal loin 34–36, and the two total-time rows for tenderloin.
U.S. Department of Agriculture, Food Safety and Inspection Service. A work of the United States Government and in the public domain. Roasting Those “Other” Holiday Meats. fsis.usda.gov. Lamb leg bone-in 5–9 lb at 20–26 min/lb — the row this page uses — plus capon, goose, duck, Cornish hen, pheasant and quail, and the instruction to “Add 15-30 minutes for stuffed poultry; stuffing must reach 165°F internally.” This page prints the 15–30 minute figure and the 165 °F stuffing minimum together, because neither means anything without the other.
U.S. Department of Agriculture, Food Safety and Inspection Service. A work of the United States Government and in the public domain. Let’s Talk Turkey — A Consumer Guide to Safely Roasting a Turkey. fsis.usda.gov. “Set your oven temperature no lower than 325 °F”, the full 325 °F timetable for unstuffed and stuffed birds by weight band, and the instruction to check “the innermost part of the thigh and wing and the thickest part of the breast”. The whole non-proportionality argument on this page is derived from this one table: its own minutes per pound fall from 17.3 at 10 lb to 13.0 at 22 lb.
Food Standards Agency (UK). Safer Food, Better Business for caterers: Cooking safely. food.gov.uk. The equivalent time/temperature combinations — 60 °C for 45 minutes, 65 °C for 10 minutes, 70 °C for 2 minutes, 75 °C for 30 seconds, 80 °C for 6 seconds — and the instruction to check the thickest part. All five lie on one thermal-death-time line with a z value of 7.5 °C, which this page computes rather than assumes.
Reed’s Butchers. A Guide to Roasting Beef Joints. reedsbutchers.co.uk. The British convention in a named butcher’s own words: 20 minutes per 450 g for rare, 25 for medium, 30 for well done, “plus 20 minutes extra”, with target centre temperatures of about 50–52 °C rare, 55 °C medium rare, 60 °C medium and “closer to 70 °C” well done. Those doneness temperatures are a British butcher’s, not a food-safety authority’s; the FSIS minimum is the one this page quotes.
Carslaw HS, Jaeger JC. Conduction of Heat in Solids, 2nd edn, Oxford. The result this page uses is the elementary one: the time for the centre of a body to reach a given temperature scales as the square of its characteristic length, so as the two-thirds power of its mass at constant shape. The textbook was not fetched; the scaling was obtained instead by solving the heat equation numerically in a slab and confirming that doubling the thickness quadruples the time, and the exponent was then compared with the one fitted to the FSIS turkey chart (0.649).