Cooking Time Scaler Formula

Understand the math behind the cooking time scaler. Each variable explained with a worked example.

Use the Cooking Time Scaler

Formulas Used

Minutes Per Pound

minutes_per_lb = time_per_lb

Estimated New Time

new_time_min = time_per_lb * new_weight

New Time (hours)

new_time_hours = (time_per_lb * new_weight) / 60

Variables

VariableDescriptionDefault
original_weightOriginal Weight(lb)4
original_time_minOriginal Cooking Time(min)120
new_weightNew Weight(lb)6
time_per_lbMinutes per pound= original_time_min / original_weightcalculated

How It Works

How Cooking Time Scales With Weight

Cooking time scales roughly linearly with weight for most roasts and whole cuts. A 10-lb roast at 325°F takes about twice as long as a 5-lb roast at the same temperature. But it's not perfectly linear. Larger cuts have more mass relative to surface area, so heat penetrates slower per pound.

The Basic Formula

Total Time = Weight (lbs) x Minutes Per Pound

Minutes per pound varies by meat type and desired doneness. Beef at rare is about 15 min/lb, medium is 20 min/lb. Pork runs 20-25 min/lb. Chicken is around 20 min/lb at 375°F.

When to Use This

You have a recipe that says "cook a 5-lb roast for 2 hours" but you bought a 7-lb roast. Scale the time proportionally: 7/5 x 120 minutes = 168 minutes (about 2 hours 48 minutes). Works for beef, pork, lamb, chicken, and turkey.

Why a Thermometer Matters More Than a Timer

Every oven runs differently. Your 350°F might be someone else's 335°F. Altitude, starting temperature of the meat (fridge-cold vs. room temp), and pan material all affect cooking time. Use the scaled time as a guide, but pull the meat when a probe thermometer reads your target internal temperature. For beef medium-rare that's 135°F, for pork it's 145°F, for chicken it's 165°F.

Common Mistakes

  • Not resting the meat after cooking. Internal temperature rises 5-10°F during rest. Pull it out slightly early.
  • Opening the oven door repeatedly to check. Each opening drops the temperature by 25-50°F and adds cooking time.
  • Scaling time for stuffed poultry the same way as unstuffed. Stuffed birds need about 15 extra minutes per pound because the stuffing insulates the cavity.

    • Worked Example

    A 4 lb roast takes 120 minutes. How long for a 6 lb roast?

    original_weight = 4original_time_min = 120new_weight = 6
    1. 01Minutes per pound: 120 / 4 = 30 min/lb.
    2. 02New time: 30 x 6 = 180 minutes (3 hours).
    3. 03Use a meat thermometer to verify doneness.

    Frequently Asked Questions

    Does cooking time scale linearly with weight?

    Approximately, but not exactly. Larger roasts may cook slightly faster per pound because the surface area to volume ratio decreases. Use a thermometer.

    Should I change oven temperature?

    Generally keep the same temperature. Only adjust if the surface is browning too fast (tent with foil) or not browning enough (increase for the last 15 minutes).

    What about resting time?

    Larger roasts need more resting time. Allow 15-20 minutes for a 4 lb roast and 30-45 minutes for a large turkey.

    Ready to run the numbers?

    Open Cooking Time Scaler