Scaling recipe portions: how the math works
A simple rule of three for any ingredient list
Whether you want to stretch a recipe for 4 people to feed 6 guests, or halve a family-size portion for two people: the conversion always follows the same rule-of-three formula: new amount = old amount × (new servings ÷ old servings). The ratio between the new and old number of servings is called the scaling factor and is applied to every single ingredient.
Our calculator performs this calculation for your entire ingredient list at once and live: you enter the name, amount and unit of each ingredient, choose the serving counts, and immediately see all the converted amounts.
Example: scaling a recipe from 4 to 6 servings
| Item | Amount |
|---|---|
| Formula | old amount × (new servings ÷ old servings) |
| Scaling factor | 6 ÷ 4 = 1.5 |
| Flour (250 g) | 250 g × 1.5 |
| Result flour | 375 g |
| Milk (300 ml) | 300 ml × 1.5 |
| Result milk | 450 ml |