Hydration content considering other ingredients?
I understand that hydration percentage is important and it varies with type of bread. But how do you calculate it considering other ingredients. For example, For example I have a recipe that requires flour, oats, wheat germ, gluten, maple syrup, oil, cinnamon, buttermilk plus salt and yeast. I want to cut the recipe in half or to one-third. I know you can't just mathematically cut everything. So how do you calculate hydration levels considering other ingredients.