On January 1, 2019, maintenance (also know as alimony) is calculated differently than it had been calculated before this date. Here is the Illinois law, 750 ILCS 5/504.
But this page is not so easy to read (and it’s in Courier, no less).
I haven’t found an online calculator that I can direct my clients to that I liked, so I created one.
The two numbers you need to use this form are the Payor and Payee’s NET (not gross) annual (not monthly) incomes.
The Payor is the person paying the maintenance.
The Payee is the person receiving the maintenance.
And again, these numbers need to be net annual incomes for each party. So the income you get after taxes and deductions and other things get pulled out.
This is quick build so let me know if it does not work for you. firstname.lastname@example.org