The recipe scaling formula
Use this formula before you touch a measuring cup:
Scaling factor = target servings / original servings. Multiply each ingredient quantity by that factor.
For example, a recipe written for 4 servings that needs to serve 6 has a factor of 6 / 4 = 1.5. One and a half cups of stock becomes 2.25 cups. Keep the ingredient quantities, the serving count, and the original formula together so the calculation can be checked later.
Worked serving conversions
| Change | Factor | 1 cup becomes | 2 eggs become |
|---|---|---|---|
| 4 to 6 | 1.5 | 1 1/2 cups | 3 eggs |
| 6 to 10 | 1.67 | 1 2/3 cups | 3 1/3 eggs |
| 8 to 12 | 1.5 | 1 1/2 cups | 3 eggs |
| 8 to 4 | 0.5 | 1/2 cup | 1 egg |
The decimal factors are rounded for print; the working arithmetic should retain the original fraction where possible. A six-to-ten conversion is exactly 10/6, or 5/3, not an endlessly repeating approximation.
What not to multiply
Cooking time and oven temperature
Doubling a batter does not mean doubling the baking time. A deeper pan may need a lower temperature and a longer bake, while a wider pan can brown sooner. The correct setting depends on pan dimensions, batter depth, oven airflow, and the recipe's intended doneness.
Pan size
Choose a pan that keeps the batter depth reasonably close to the original. Two 8-inch cake layers, for instance, are not equivalent to one 16-inch layer: the larger pan has very different heat penetration and surface area.
Salt and spices
Start with about 80 percent of the scaled amount when tasting is possible, then adjust. This is a practical starting point rather than a fixed law. A dish that reduces heavily may concentrate salt, while a larger volume of bland liquid may need more seasoning.
Leaveners
Baking powder, baking soda, and yeast are not merely volume ingredients. Their effect depends on acidity, hydration, temperature, and time. Check the original formula or a tested reference before making a large change.
Fractions in a real kitchen
Recipe scaling produces awkward numbers because ingredients and servings do not always share convenient factors. Two eggs multiplied by 5/3 is 10/3, or 3 1/3 eggs. For an accurate partial egg, whisk the whole egg, weigh it, and use the proper fraction by weight.
For dry ingredients, converting a cup to grams by ingredient is often more reliable than stacking a fraction on a volume measurement. One cup of flour is not one cup of sugar in weight, and the error grows with a larger batch.
Paste the whole recipe and let the Recipe Converter separate ingredients from instructions.
Open the recipe converterRelated recipe tools
- Ingredient Converter for cups, tablespoons, ounces, grams, and milliliters.
- Convert Recipe to Metric for US-to-metric recipe conversion.
- Cups to Grams for ingredient-specific weight references.
- Oven Temperature Converter for conventional, fan, and Gas Mark settings.