This Illinois alimony calculator makes Illinois maintenance calculations using the Illinois alimony formula. This calculator is intended to be used only as a general tool to estimate potential splits and payments.To calculate Illinois guideline maintenance, you must enter gross income, child dependent, and marriage length information into the calculator. For more information on estimating your spousal maintenance or alimony amount, feel free to use our Illinois alimony payment estimator. Get an estimate for alimony payments and duration. Get an idea on how much money a month you can expect to pay, and for how you can expect to pay it. Calculate alimony quickly and accurately with our state-specific alimony calculators. Get an estimate based on your state's guidelines for free. Estimate Alimony Payments. Find out what judges consider when deciding how much alimony to award during or after divorce—and when courts use formulas to calculate spousal support.