Scale a recipe up or down to the right number of servings, and find the new amount for each ingredient.
The calculator first finds a scaling factor based on the ratio between the desired and original number of servings:
You can repeat the calculation for every ingredient in the recipe using the same scaling factor — just swap in the number for that particular ingredient. Things like spices, salt and acid (e.g. lemon juice or vinegar) should often be scaled a bit more cautiously than purely proportionally, since flavor doesn't always scale linearly. Taste as you go and adjust as needed, especially for large changes in serving count.
No. Baking time relates to heat conduction and the size of the pan, not just the amount of ingredients. A double batch usually only needs slightly longer baking time, not double — check with a toothpick test or food thermometer instead.
Not necessarily. Strong flavors like spices, salt, chili and acid (lemon, vinegar) often taste stronger than purely proportional at large amounts, so it can be worth scaling these a bit more cautiously and tasting as you go.
Calculate the scaling factor once using the original and desired number of servings. Then apply the same factor to the amount of each individual ingredient in the recipe, one by one.