About the roast time calculator
A roast time calculator turns three inputs (meat type, weight in pounds, oven temperature, and target doneness for red meat) into an estimated oven time and the corresponding pull-from-oven internal temperature. The maths approximate published USDA and Cook's Illustrated tables; the meat thermometer remains the final authority.
How it works
Roasting transfers heat from the oven air into the meat by convection at the surface and conduction through the flesh. Larger roasts take more time per pound because the temperature gradient has further to travel, but the relationship is not strictly linear. The calculator uses a "minutes per pound at 350F" baseline for each meat type, then adjusts for oven temperature and target doneness.
Time (min) = Weight x (minutes/lb + doneness_adj + temp_adj) + base_offset temp_adj = (350 - oven_temp) / 25 x 2 Pull temp = Target doneness temp minus 5F (carryover during rest) Rest = 10 to 30 minutes by size
- Carryover cooking: a resting roast keeps cooking from residual heat. Internal temperature rises 5F (small cuts) to 10F (prime rib).
- Bone-in: bone conducts heat into the centre, shaving 5 to 10 percent off boneless times.
- Tempering: pull the roast from the fridge 30 to 60 minutes before cooking so the centre is not refrigerator-cold.
Worked example
A 6-lb bone-in prime rib at 325F, target medium-rare (135F final), pull temperature 130F.
- Baseline rate: beef at 15 min/lb at 350F.
- Temperature adjustment: (350 minus 325) / 25 x 2 = 2 extra minutes per pound.
- Doneness adjustment: medium-rare = 0 minutes per pound.
- Cooking time: 6 x (15 plus 2) = 102 minutes, or 1 hour 42 minutes.
- Pull temperature: 130F (carryover lifts to ~135F during rest).
- Rest: 20 minutes loosely tented in foil before carving.
Temperature, weight, and doneness reference
| Meat | Oven temp | Minutes per pound | Pull temp | Final temp after rest | Doneness |
|---|---|---|---|---|---|
| Beef (prime rib, sirloin) | 325F (160C) | 14 to 16 | 120F (49C) | 125F | Rare |
| Beef | 325F | 15 to 17 | 130F (54C) | 135F | Medium-rare |
| Beef | 325F | 17 to 20 | 140F (60C) | 145F | Medium |
| Beef | 325F | 22 to 25 | 155F (68C) | 160F+ | Well-done |
| Lamb (leg, rack) | 350F (175C) | 15 to 18 | 130F | 135F | Medium-rare |
| Pork (loin, shoulder) | 350F | 18 to 22 | 140F | 145F | Medium (USDA safe) |
| Chicken (whole) | 350F | 20 per lb + 15 | 160F (71C) breast | 165F thigh | Safe |
| Turkey (unstuffed) | 325F | 13 to 15 | 160F breast | 165F thigh | Safe |
| Turkey (stuffed) | 325F | 15 to 17 | 165F stuffing | 165F+ | Safe |
Common pitfalls
- Skipping the rest. Carving straight out of the oven loses 20 to 30 percent of the juice to the cutting board. A 15-minute rest tents heat and lets the muscle fibres reabsorb juice.
- Cold from the fridge. A roast that goes in at 40F takes 20 to 30 percent longer than one that has tempered for an hour at room temperature.
- Probing through bone or fat. Both insulate, giving false-low readings. Probe the thickest part of the muscle, away from bone.
- Trusting "X minutes per pound" alone. A 12-lb turkey and two 6-lb birds are not equivalent: surface-to-mass ratio shifts cooking time. Use a thermometer, not the clock.
- Opening the oven repeatedly. Each peek drops oven temperature 25 to 50F and adds 5 to 10 minutes total. Use a leave-in thermometer.
- Cooking pork to leather. USDA lowered safe pork to 145F (medium) in 2011. Old "165F or grey" advice produces dry meat; today, a slight pink centre is safe in whole-muscle cuts.
Related tools and glossary
Frequently asked questions
How long do you roast chicken per pound?
At 350F (175C), roast chicken takes about 20 minutes per pound plus 15 minutes. A 4-pound chicken takes roughly 1 hour 35 minutes. Always verify with an instant-read thermometer in the thigh: pull at 165F (74C) internal temperature.
What temperature should I roast beef?
For a standard prime rib or top round roast, 325F to 350F (160 to 175C) gives an even result. For a high-heat sear-and-roast, start at 450F for 15 minutes then reduce to 325F. Pull at 125F rare, 130F medium-rare, 140F medium, or 155F well-done because carryover lifts another 5F during the rest.
Should I cover the roast with foil?
Cover loosely with foil for the first two-thirds of cooking to prevent over-browning, then remove for the final third to develop a crispy exterior. Turkey benefits from tenting with foil over the breast if the skin browns faster than the inner thigh reaches 165F.
How long should I rest a roast?
Rest small roasts and birds (chicken, lamb rack) 10 to 15 minutes. Rest large roasts (prime rib, leg of lamb, whole turkey) 20 to 30 minutes, loosely tented in foil. Resting redistributes juices and lets carryover cooking finish the centre without overshooting.
Sources
- USDA Food Safety and Inspection Service, Safe Minimum Internal Temperature Chart (2025 revision).
- Cook's Illustrated, The Science of Roasting, America's Test Kitchen.
- Harold McGee, On Food and Cooking, chapters on meat and heat transfer.
- ChefSteps, sous-vide and roast pull-temperature reference tables.