How to Scale a Recipe Up or Down Without Ruining It

Step 1: find the scale factor

scale factor = servings you want ÷ servings in the recipe

The recipe serves 6 and you need 10, so the factor is 10 ÷ 6 = 1.667. Multiply every ingredient by that same number. To scale down to 4 servings, the factor is 4 ÷ 6 = 0.667.

Notice how clean the numbers are in grams and milliliters. This is the best reason to convert cups and spoons to weights before you scale, as the next step explains.

Step 2: tame awkward amounts

Multiplying two thirds of a cup by 1.667 gives 1.11 cups, which no measuring cup shows. Convert volume measures to grams where you can, scale the grams, and weigh the result. A cups to grams converter is useful here because a cup of flour and a cup of sugar do not weigh the same.

Eggs are the classic problem. The example needs 3.33 eggs. You have two reasonable options. Round to 3 eggs and accept that the mixture is slightly less rich, or beat a fourth egg, weigh it and use a third of it. A large egg without its shell is roughly 50 g, so a third is about 17 g.

• Tiny quantities: round to the nearest measure you can actually use, such as an eighth of a teaspoon.
• Whole items such as one onion or one can: round to the nearest whole item and adjust another ingredient slightly if it matters.
• Keep a note of the rounding you made so you can repeat or correct it next time.

Step 3: match the pan by area

For cakes, bakes and sheet-pan dishes, the pan size sets how deep the mixture will be. Depth affects baking, so compare pans by area, not by width.

Worked example: a recipe written for an 8-inch round pan. The pan has a radius of 4 inches, so its area is π × 4² = 50.3 square inches. A 9-inch pan has a radius of 4.5 inches and an area of π × 4.5² = 63.6 square inches. The ratio is 63.6 ÷ 50.3 = 1.27, so you need about a quarter more batter to keep the same depth.

Rectangles work the same way. An 8 × 8 inch pan is 64 square inches and a 9 × 13 inch pan is 117, a ratio of 1.83. Making a recipe for the small pan in the large one needs nearly double the mixture.

If you bake the recipe in a pan of a different size without scaling, the layers come out thinner or thicker, and the time needs to change. The area of a circle calculator helps with round pans.

Step 4: time, heat and seasoning

Cooking time does not scale with the factor. A cake batch poured into a deeper pan does not take twice as long just because there is twice as much of it, and a doubled batch split between two pans of the original size takes about as long as the original. Keep the oven temperature from the original recipe, use the stated time as a starting point, and test for doneness by the signs the recipe describes, such as a skewer coming out clean or a set center.

A thinner layer cooks faster and a deeper one slower, so check early when you spread the mixture thinner. For stovetop dishes, a larger pot has a different surface area, which changes how fast liquid evaporates. Expect to adjust simmering time and taste before you serve.

Seasoning, spices and leavening are the places where straight multiplication is least reliable once you scale far from the original. Many cooks add salt and strong spices in stages, starting with a little less than the scaled amount and tasting. For large changes, scale the main ingredients first and the seasoning last.

If the recipe is very sensitive, such as delicate bakes or bread, consider making two batches of the original rather than one scaled-up batch.

Let a tool do the arithmetic

Paste the ingredient list into the recipe scaler with the original and target servings, and it multiplies every line and can convert units at the same time. You still make the judgment calls about eggs, pans and timing, but the multiplication is done correctly.