Scale Recipes

Scaling recipes

When a recipe is changed to serve more or fewer people, every ingredient must be changed by the same factor. The key idea is proportionality: if one amount is multiplied, all linked amounts are multiplied by that same number.

Method

1. Find the scale factor. Compare the new serving size with the original one. For example, if the recipe is doubled, the factor is 2; if it is cut in half, the factor is (\tfrac12).
2. Multiply each ingredient by the factor. Use exact arithmetic with fractions, decimals, or whole numbers as needed.
3. Simplify the result. Reduce fractions and write answers in their simplest exact form.

Example idea

If an ingredient is (\tfrac34) cup and the recipe is tripled, compute [ \tfrac34 \times 3 = \tfrac94 = 2\tfrac14. ] Both forms are exact, but the simplified exact answer is usually preferred.

Check

A good check is to see whether all ingredients were scaled by the same factor. The ratios between ingredients should stay the same as in the original recipe. If one amount looks too large or too small compared with the others, recheck the multiplication.