This is the fun part! The part where you get to determine what you will have to live on once you are divorced. You are aware of what it takes to run the household now. What you need to know is what your costs of living will be after the divorce. Some people's incomes drops drastically after divorce. It’s best you be prepared by building a budget now instead of being hit over the head with bills you can’t pay.
You will have to estimate some expenses but it is important so that you can have some idea of what you will need to survive in your new life. It is also important because it will influence how you negotiate your divorce settlement. You need to know what you will need financially in order to evaluate your settlement options or what you may ask for should your case go to court.