Recipe Scaling (Ingredient for a New Yield)

Ingredients scale linearly with servings, so a recipe for four becomes a recipe for six by multiplying every quantity by $6/4$. That much is just proportion, and it is the part a calculator can do for you.

The part it cannot do is everything else in the kitchen. Cooking time does not scale, because heat has to travel into the middle of the food and a doubled loaf is not twice as thick. Pan size scales with area rather than volume, so doubling a cake batter and pouring it into the same tin gives you a raw centre and a burnt rim. Salt, leavening and spice usually want less than a full multiple, since perception is nonlinear and a tripled recipe rarely wants triple the chili. Evaporation scales with surface area too, which is why a doubled sauce reduces more slowly and a doubled pot of rice needs proportionally less water.

Scale the ingredients with the arithmetic, then adjust the seasoning by taste and the timing by testing. Bakers who need real precision go further and work in baker's percentages, where every ingredient is quoted as a fraction of the flour mass and the recipe becomes scale-free by construction.