How to Scale a Recipe
Divide your desired servings by the original servings to get the scaling factor. Multiply each ingredient amount by that factor. A recipe for 4 scaled to 6 = multiply everything by 1.5.
Most ingredients scale linearly. The exceptions: spices and salt (scale by 75% instead of 100% for doubling), leaveners like baking powder (scale carefully — too much ruins texture), and cooking time (doesn't change much when scaling up, but check doneness).
FAQ
Do cooking times change when scaling?
Mostly no. A doubled cake batter in the same pan size needs more time, but a doubled soup in a bigger pot takes roughly the same. Always check internal temperature for meat.
Can I halve a recipe that calls for 1 egg?
Beat the egg, measure it (about 3 tablespoons total), and use half. Or use 1 egg yolk for richness or 1 egg white for structure, depending on the recipe.