Illinois has established a specific formula for calculating the amount and duration of spousal maintenance obligations or awards. Estimate Alimony Payments.Illinois uses a formula outlined in the Illinois Marriage and Dissolution of Marriage Act to calculate spousal maintenance. This calculator is intended only to give a general idea of spousal maintenance calculations. Chicago Spousal Maintenance Calculator. Alimony (or spousal maintenance) can play an important role in your post-divorce financial situation. To calculate Illinois guideline maintenance, you must enter gross income, child dependent, and marriage length information into the calculator. New 2022 Illinois Maintenance Calculator. This 2022 Illinois alimony calculator makes Illinois alimony calculations. Under the Illinois Statutes, you may be entitled to alimony to help ensure you are provided for in the aftermath of a divorce and to aid in your recovery.