How to Calculate Roasting Time by Weight
Roasting time is calculated as minutes per pound (or minutes per kilogram) multiplied by the weight of the meat. This calculator uses tested guidelines from the USDA and established culinary sources for each meat type and doneness level. Times shown assume the meat starts at room temperature (removed from the refrigerator 30–60 minutes before cooking).
Always verify doneness with a calibrated instant-read thermometer inserted into the thickest part of the meat, away from bone. Internal temperature is the only reliable way to confirm food safety — cooking time alone is not sufficient.
Safe Internal Temperature Guide
- Beef roast: 125°F (52°C) rare, 145°F (63°C) medium, 160°F (71°C) well done.
- Whole chicken and turkey: 165°F (74°C) measured in the thickest part of the thigh.
- Pork loin: 145°F (63°C) with a 3-minute rest.
- Lamb leg: 145°F (63°C) for medium-rare, 160°F (71°C) for medium.
- Pre-cooked ham (reheating): 140°F (60°C).
Tips for Even Roasting
The weight-based time formula is a starting point, not an exact prescription. Many variables affect cooking time, including oven calibration, the starting temperature of the meat, the shape of the roast, whether the meat is boned or boneless, and how many times you open the oven door. Using a leave-in probe thermometer gives you real-time feedback and eliminates guesswork.
- Rest the meat: let large roasts rest 15–30 minutes after removing from the oven. Internal temperature rises by 5–10°F (carryover cooking).
- Tent loosely with foil during resting to retain heat without steaming the crust.
- A heavy roasting pan with a rack promotes even air circulation and better browning.
- Pat the meat dry before seasoning for better Maillard browning on the exterior.
Frequently Asked Questions
How long does a 15 lb turkey take to cook?
An unstuffed 15 lb turkey at 325°F takes approximately 2.75 to 3.25 hours using 11 minutes per pound (the rate for turkeys over 14 lb). Always check that the thigh reaches 165°F before removing from the oven. A stuffed turkey takes 30–45 minutes longer.
Should I cook a roast from room temperature or cold?
Removing a large roast from the refrigerator 30–60 minutes before cooking helps it cook more evenly, reducing the overcooked outer layer. For food safety, do not leave meat at room temperature for more than 2 hours. This calculator assumes room-temperature meat; add 10–15 minutes per pound if cooking straight from cold.
What is carryover cooking?
Carryover cooking is the continued rise in internal temperature after a roast is removed from the oven. Heat stored in the outer layers continues to flow toward the cooler centre. For a large beef roast, internal temperature can rise 5–10°F during a 20-minute rest. Pull the meat from the oven when it is 5–10°F below your target temperature to avoid overcooking.