In the US, food products have an ingredient list and a "Nutrition Facts" panel. The ingredient list lists all ingredients in order from most abundant to least abundant, e.g. "flour" would be the first ingredient for bread and "salt" would be further down the list. The Nutrition Facts shows the abundance of macronutrients (protein, carbohydrate, fat) and micronutrients (minerals, vitamins) in the product. Reliable nutritional information on ingredients is readily available online from the US Government. What calculations would be necessary to reconstruct a recipe from nutritional data on the product and its ingredients and the ordered list of its ingredients? So, maybe your bread contains flour, sugar, butter, yeast, and salt, listed in that order. You would start with the nutritional content of each of the ingredients and the nutritional information on the product and calculate the amount of ingredients in the bread, i.e. 6 cups flour, 2/3 cup sugar, 1/4 cup butter, 1-1/2 tsp salt. Assume the yeast has no effect on the figures and use the amount of yeast recommended on the package.