Cooking Time Calculator
Adjust cooking times when scaling a recipe up or down. Enter the original weight and time, then the new weight, and this calculator applies the scientific 2/3 power scaling rule for accurate results.
How Cooking Time Scales With Weight
A common mistake is assuming that doubling the weight means doubling the cooking time. In reality, cooking time scales with the two-thirds power of the weight ratio. This is because heat transfer depends on surface area, which grows more slowly than volume as an object gets larger.
The formula our calculator uses is:
New Time = Original Time × (New Weight / Original Weight)0.67
For example, if a 5 lb roast takes 2 hours, an 8 lb roast of the same cut takes approximately 2 hours and 43 minutes — not 3 hours and 12 minutes as a simple linear scaling would suggest. This non-linear relationship is why so many home cooks either undercook or overcook when they change recipe sizes.
Why a Meat Thermometer Matters More Than Time
Calculated cooking times are estimates, not guarantees. Variables like oven accuracy, starting temperature of the meat, altitude, and the shape of the cut all affect actual cooking time. The only reliable way to know when meat is done is to check the internal temperature:
- Poultry (chicken, turkey): 165°F (74°C)
- Ground meat: 160°F (71°C)
- Beef, pork, lamb (steaks/roasts): 145°F (63°C) with a 3-minute rest
- Fish: 145°F (63°C)
Use a digital instant-read thermometer inserted into the thickest part of the meat, away from bone, for the most accurate reading.
Common Cooking Temperatures by Method
When adjusting cooking time for different weights, keep the temperature the same as the original recipe. Here are standard temperatures for common cooking methods:
- Low and slow roasting: 275°F to 325°F — ideal for tough cuts that need time to break down collagen
- Standard roasting: 350°F to 375°F — the workhorse temperature for most meats and casseroles
- High-heat roasting: 400°F to 450°F — great for crispy skin on poultry and quick-cooking vegetables
- Broiling: 500°F+ — direct high heat for browning and finishing