Illinois law offers formulas for how much spousal support you will pay or receive in a divorce. Call a Joliet alimony lawyer at .Spousal support is now calculated using two main factors: the net income of the spouses and the length of the marriage. How Is Spousal Support Calculated in Illinois? In Illinois there are five main types of alimony or spousal support; temporary, fixedterm, reviewable, permanent, and lumpsum. Not all divorces include an order to pay alimony. Illinois law has set specific criteria for awarding and determining spousal maintenance. Calculate your Illinois child support amount with our free calculator. Please read Establishing parentage (paternity) before beginning the next steps. In Illinois, either party to a divorce can be entitled to receive maintenance – which used to be called "spousal support" or "alimony.