Illinois has established a specific formula for calculating the amount and duration of spousal maintenance obligations or awards. This Illinois alimony calculator makes Illinois maintenance calculations using the Illinois alimony formula.Chicago Spousal Maintenance Calculator. Alimony (or spousal maintenance) can play an important role in your post-divorce financial situation. Use our Chicago alimony calculator to determine if you may be entitled to alimony and the amount you are likely to receive. Illinois uses a formula outlined in the Illinois Marriage and Dissolution of Marriage Act to calculate spousal maintenance. Divorce and alimony calculator. Estimate your spousal and child support, and division of assets and debts. In Illinois, maintenance supports spouses postdivorce. For expert guidance on maintenance and divorce, consult Chicago family law attorney.