Start with the scaling ratio
Find your factor: divide the servings you want by the servings the recipe makes. Cooking two portions of a four-portion recipe is a factor of 0.5; doubling is 2. Multiply each ingredient by that factor.
For most ingredients — proteins, vegetables, grains, liquids — straight multiplication works perfectly.
Handle the ingredients that don't scale linearly
A few things need judgment rather than multiplication:
Salt and strong spices: scale to about ¾ of the factor, then taste and adjust
Leavening (baking soda/powder): scale carefully — too much ruins texture
Oil for frying: you need enough to coat the pan, not a strict multiple
Adjust the equipment, not just the amounts
Double a recipe and it may not fit one pan. Crowding a skillet steams food instead of browning it. Use a bigger pan or cook in batches so the food behaves the same way it did at the original size.
Cook times change less than you think
Scaling quantities rarely doubles cook time. A larger roast takes somewhat longer; a doubled pot of soup takes a little longer to come to a boil, but simmer times are similar. Judge doneness by temperature and texture, not the clock.
Let software do the math
The easiest way to scale a recipe is to not do the arithmetic at all. A portion slider recalculates every ingredient instantly and updates your shopping list to match, so what you cook and what you buy always line up.
Frequently asked questions
How do I scale a recipe to a different number of servings?
Divide the servings you want by the servings the recipe makes to get a factor, then multiply each ingredient by it. Most ingredients scale linearly; season strong spices and salt to about three-quarters of the factor and adjust to taste.
Does cooking time change when you scale a recipe?
Less than you'd expect. Larger quantities take somewhat longer to heat through, but simmer and bake times are usually similar. Judge doneness by temperature and texture rather than simply multiplying the time.
What is the easiest way to scale a recipe?
Use a recipe tool with a portion slider that recalculates ingredients automatically and updates your shopping list, so you avoid the math and your quantities always match what you buy.