MinuteMetric

Everyday Household Calculations

These are the small calculations that come up constantly and are annoying every time: scaling a recipe for a different number of people, converting a pan size, working out a roasting time for an unusual joint, splitting a shared bill, or estimating what a pet actually costs to feed over a year.

Cooking calculations deserve a word of caution, because they don't all scale the same way. Ingredient quantities scale linearly — double the people, double the flour. Cooking times do not. A joint of twice the weight is not twice as thick, and heat penetrates by thickness rather than mass, so doubling the meat adds far less than double the time. Baking is fussier still: changing pan dimensions changes batter depth, which changes both time and temperature. Use calculated times as a starting point and finish by testing the food itself — a thermometer in the meat beats any formula.

Rules of Thumb Worth Knowing

• Cook to temperature, not time. Times estimate; internal temperature measures. For anything where food safety matters, the thermometer decides.
• Rest cooked meat. Internal temperature continues rising after it leaves the oven, and resting lets juices redistribute.
• Scale seasoning cautiously. Salt, spice and leavening often don't scale linearly. Add proportionally less at first and adjust to taste.
• Weigh where precision matters. Volume measures for flour vary hugely with how the cup was filled. Baking is much more reliable by weight.