Cooking conversions translate between measurement systems (cups to milliliters, ounces to grams, tablespoons to teaspoons) so that any recipe from any source can be followed accurately. Scaling a recipe — doubling, halving, or adjusting to a different serving count — requires understanding which ingredients scale linearly (most do) and which do not (leavening agents, salt, and spices often need less-than-proportional increases). Weight-based measurements are more reliable than volume for dry ingredients because packing density varies.
Memorize the core equivalents first (1 cup = 240 mL, 1 oz = 28 g, 3 tsp = 1 tbsp, 16 tbsp = 1 cup) and keep a conversion chart posted in the kitchen. Practice by halving a familiar recipe, then doubling it, noting where the results differ from expectations. Use a kitchen scale to weigh flour measured by volume versus by weight and observe the variance.
Cooking a recipe as written is straightforward, but two skills open up far more flexibility: converting between measurement systems and scaling recipes up or down. Both rely on the ratio and proportion concepts you've already learned — applied to a practical, edible context.
Unit conversions are chain multiplications. The key equivalents to have in memory are: 3 teaspoons = 1 tablespoon, 16 tablespoons = 1 cup, 1 cup ≈ 240 mL (US), and 1 ounce ≈ 28 grams. To convert, multiply by a fraction equal to 1 — for example, to convert ¾ cup to tablespoons: ¾ cup × (16 tbsp / 1 cup) = 12 tablespoons. The units cancel just like variables in algebra. When a recipe from a different country uses metric measurements, the same chain-multiplication approach applies; the only trap is that "cup" means different volumes in US, UK, and Australian recipes, so weight-in-grams is far more reliable for anything precision-sensitive.
Scaling is proportional reasoning applied to ingredients. To scale a recipe, calculate your scale factor (desired servings ÷ original servings) and multiply every ingredient quantity by that factor. Most ingredients — flour, sugar, butter, eggs, liquids — scale linearly and perfectly. A 2× recipe simply uses twice as much of each. This is the rule for the majority of what you'll scale.
The exceptions matter most in baking. Leavening agents (baking powder, baking soda, yeast) do not scale linearly: doubling a recipe doesn't require doubling the leavening. Too much leavening makes baked goods taste bitter or collapse after rising too fast. The standard guidance is to use about 75–80% of the proportional amount when scaling up significantly. Salt and strong spices behave similarly — scale them conservatively and adjust to taste. Cooking time and temperature almost never scale with batch size; a larger pan or more portions usually needs the same temperature but requires checking doneness empirically.
Finally, the hidden variable in all of this is measurement precision. Volume measurements — especially of dry ingredients — are surprisingly unreliable because packing density varies. A "cup" of flour can range from 120 g (lightly spooned) to 160 g (scooped and packed) depending on technique. For everyday cooking, this variation is harmless. For baking, where the ratio of flour to liquid determines whether your cake rises or turns to a brick, it matters enormously. A kitchen scale measuring in grams removes this uncertainty completely, which is why professional bakers almost never use volume for dry ingredients. When you read a recipe in grams, trust it — it's being precise on purpose.