How do you use percentages in a bakery situation? Always multiply by weight%.The most common application is with recipes, some others are costs, budgets etc.Because flour is normally the base ingredient and largest measure in a recipe it is expressed as being 100%, and all other ingredients in the recipe are expressed as a percentage of the flour weight.E.g: 3kg of flour in the recipe, with sugar added at the rate of 10%.This means that the amount of sugar to be used is 10% of the flour weight of 3kg.To calculate the amount of sugar:3.000 x 10% = 0.3