The Illinois Maintenance Calculator estimates court-guideline spousal support under 750 ILCS 5/504. Enter the payor’s and payee’s annual net incomes and the length of your marriage to get a maintenance amount estimate and guideline duration — helping you prepare for negotiation or understand what Illinois family courts may award.
Illinois Law · 750 ILCS 5/504
Spousal Maintenance Calculator
Estimate guideline maintenance amount & duration based on Illinois statutory formula
This tool provides estimates only based on Illinois guideline formulas. Results are not legal advice. Consult a licensed attorney for your specific situation.
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What Is Illinois Maintenance?
Illinois maintenance — also referred to as alimony in Illinois or spousal support — is court-ordered financial support paid by one spouse to the other following a marital dissolution. Unlike child support, which is tied to the needs of children, Illinois divorce maintenance is designed to address economic disparities between spouses after a marriage ends.
Illinois courts determine maintenance under the Illinois Marriage and Dissolution of Marriage Act, specifically 750 ILCS 5/504. When the combined gross income of both spouses is below $500,000, Illinois law provides a statutory maintenance formula that judges use as a starting point. For marriages with combined gross income above that threshold, courts exercise broader discretion without being bound to the guideline formula.
This family law calculator focuses on the guideline formula — the formula most commonly applied when parties earn within that $500,000 combined threshold.
Illinois Maintenance Formula: How It's Calculated?
The Statutory Maintenance Formula
The statutory maintenance formula under Illinois maintenance guidelines produces an annual maintenance amount estimate using the following calculation:
Annual Maintenance = (33.33% × Payor’s Net Income) − (25% × Payee’s Net Income)
Both figures use annual net income — income after taxes and mandatory deductions — not gross income. The result is the guideline maintenance amount per year, typically expressed as a monthly payment.
The 40% Combined Income Cap
A critical limit applies: the payee spouse’s total annual income after receiving maintenance cannot exceed 40% of the combined net income of both spouses. If the formula result would push the payee above that threshold, the maintenance amount is reduced until the payee’s total (payee net income + maintenance) equals exactly 40% of combined net income.
Combined Net Income = Payor Net Income + Payee Net Income
Maximum Payee Total = 40% × Combined Net Income
Capped Maintenance = Maximum Payee Total − Payee Net Income
The lower of the formula result or the capped result is the guideline maintenance amount.
Gross Income vs. Net Income for the $500,000 Threshold
The $500,000 threshold uses combined gross income (pre-tax), while the maintenance calculation itself uses net income (after-tax). The calculator handles both: enter gross income figures in Section 03 to verify whether the guideline formula applies, and enter annual net income in Section 01 for the actual maintenance computation.
Duration Reference Table: Maintenance Length by Marriage Length?
Illinois maintenance guidelines set guideline duration as a percentage of the length of the marriage. These are guideline multipliers under 750 ILCS 5/504 — a court may deviate based on the circumstances of the specific case.
Years Married | Duration Multiplier | Example: 10-year marriage |
Under 5 years | 0.20 | 2.0 years |
5–6 years | 0.24 | — |
6–7 years | 0.28 | — |
7–8 years | 0.32 | — |
8–9 years | 0.36 | — |
9–10 years | 0.40 | 4.0 years |
10–11 years | 0.44 | — |
11–12 years | 0.48 | — |
12–13 years | 0.52 | — |
13–14 years | 0.56 | — |
14–15 years | 0.60 | — |
15–16 years | 0.64 | — |
16–17 years | 0.68 | — |
17–18 years | 0.72 | — |
18–19 years | 0.76 | — |
19–20 years | 0.80 | — |
20+ years | Court discretion — maintenance may be permanent | — |
For marriages of 20 years or more, the Illinois statute gives the court discretion to order maintenance for a period equal to the length of the marriage or indefinite maintenance, depending on the factors of the case.
How to Use the Illinois Maintenance Calculator: Step-by-Step Guide?
The calculator interface has three input sections. Work through them in order based on what you see in the tool.
- Section 01 — Income Information: Enter the payor’s annual net income (the spouse who will pay support) and the payee’s annual net income (the spouse who will receive support). Use after-tax, after-deduction figures — not gross salary. For example, if the payor earns $150,000 gross and takes home $105,000 after taxes, enter $105,000.
- Section 02 — Marriage Duration: Enter the total number of complete years married and any additional months. The calculator converts the total duration into a decimal (e.g., 12 years 6 months = 12.5 years) and applies the appropriate duration multiplier from the Illinois maintenance guidelines table.
- Section 03 — Gross Income (for Guideline Threshold): Enter both spouses’ annual gross incomes. This section checks whether your combined gross income falls below the $500,000 guideline threshold. If your combined gross exceeds $500,000, the statutory maintenance formula may not apply and the tool will flag this; a family law attorney should be consulted for above-threshold cases.
- Click “Calculate Maintenance”: The tool outputs an estimated annual and monthly maintenance amount, the guideline duration in years and months, and a note on whether the 40% combined income cap affected the result.
Worked Example 1: Standard Formula, No Cap
Scenario: Payor annual net income: $90,000. Payee annual net income: $30,000. Marriage length: 12 years.
Step 1 — Calculate formula amount:
33.33% × $90,000 = $30,000
25% × $30,000 = $7,500
Formula result: $30,000 − $7,500 = $22,500/year ($1,875/month)
Step 2 — Check the 40% combined income cap:
Combined net income: $90,000 + $30,000 = $120,000
40% cap: $120,000 × 0.40 = $48,000
Payee total with maintenance: $30,000 + $22,500 = $52,500 → exceeds cap
Step 3 — Apply cap:
Maximum maintenance: $48,000 − $30,000 = $18,000/year ($1,500/month)
Guideline duration: 12 years × 0.52 multiplier = 6.24 years (approximately 6 years, 3 months)
Result: Estimated guideline maintenance is $1,500/month for approximately 6 years and 3 months.
Worked Example 2: Lower Income Spread, No Cap Triggered
Scenario: Payor annual net income: $72,000. Payee annual net income: $36,000. Marriage length: 8 years.
Step 1 — Formula:
33.33% × $72,000 = $23,998
25% × $36,000 = $9,000
Formula result: $23,998 − $9,000 = $14,998/year (≈ $1,250/month)
Step 2 — Cap check:
Combined: $108,000. 40% cap: $43,200.
Payee total: $36,000 + $14,998 = $50,998 → exceeds cap
Step 3 — Apply cap:
$43,200 − $36,000 = $7,200/year ($600/month)
Duration: 8 years × 0.36 = 2.88 years (approximately 2 years, 10 months)
Result: Estimated guideline maintenance is $600/month for approximately 2 years and 10 months.
Factors That Affect Your Maintenance Estimate
The statutory maintenance formula provides a starting point, not a guaranteed number. Illinois family courts consider several factors that may lead a judge to deviate from the guideline amount or duration:
- Maintenance eligibility — Courts first consider whether maintenance is appropriate at all, based on each spouse’s income, needs, and ability to become self-supporting.
- Standard of living — The standard of living established during the marriage is weighed, particularly in long marriages.
- Duration of the marriage — A short marriage where both spouses are self-supporting may result in no maintenance award, even if the formula produces a positive number.
- Each spouse’s employability — Education, job history, career interruptions (e.g., a spouse who stopped working to raise children), and realistic earning capacity all influence the award.
- Contributions to the other’s career — If one spouse supported the other through professional school or advanced training, courts treat this as a relevant factor.
- Age and health — A spouse with a disability or chronic health condition affecting earning capacity may receive a higher award or longer duration.
- Support obligations from prior relationships — Existing child support or maintenance obligations from previous divorces affect the available net income figures.
- Temporary maintenance — Courts may order temporary maintenance during the divorce proceedings, separate from the final divorce financial settlement. Temporary orders are governed by different standards and don’t necessarily predict the final award.
- Tax considerations — For divorce agreements finalized after December 31, 2018, maintenance payments are no longer deductible by the payor or taxable income for the payee under federal law. This changed the real economic impact of any given maintenance amount.
Glossary of Key Terms
- Maintenance (Illinois): The Illinois legal term for what is commonly called alimony in Illinois or spousal support. “Alimony” appears in federal tax law and common usage; Illinois statute uses “maintenance.”
- Payor: The spouse ordered to make maintenance payments.
- Payee: The spouse who receives maintenance payments.
- Net income: Income after taxes and mandatory deductions. The Illinois maintenance formula uses net income, not gross (pre-tax) income, for the maintenance calculation itself.
- Gross income: Pre-tax income. Used only for the $500,000 combined threshold check.
- 750 ILCS 5/504: The specific section of the Illinois Marriage and Dissolution of Marriage Act that governs the statutory maintenance formula, duration guidelines, and the factors courts consider.
- 40% combined income cap: A statutory ceiling that prevents the payee’s total income (payee’s net income plus maintenance received) from exceeding 40% of the spouses’ combined net income.
- Marital dissolution: The legal term for divorce in Illinois.
Common Mistakes to Avoid
- Using gross income instead of net income for the formula. The statutory maintenance formula requires net income (after taxes). Entering gross figures will significantly overstate the maintenance amount. Enter gross only in Section 03 for the threshold check.
- Ignoring the 40% cap. Many users calculate the formula result and stop there. The 40% combined income cap frequently reduces the final number — always verify both calculations.
- Treating the result as a court order. This tool produces a maintenance amount estimate only. Judges in Illinois family court have discretion to deviate from the guideline based on the factors listed in 750 ILCS 5/504(a). The estimate is a useful negotiation baseline, not a binding outcome.
- Forgetting months in the marriage duration. An extra six months can shift the duration multiplier, especially near the boundary years (e.g., 14 years 11 months vs. 15 years 1 month).
- Assuming the guideline applies to incomes over $500,000. If combined gross income exceeds $500,000, the court exercises broader discretion. The statutory formula no longer controls.
Not accounting for post-2018 tax rules. The Tax Cuts and Jobs Act of 2017 eliminated the alimony deduction for agreements finalized after December 31, 2018. Net income after taxes is now the correct baseline for both spouses.
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Frequently Asked Questions
Illinois maintenance is calculated using the statutory formula under 750 ILCS 5/504: take 33.33% of the payor's annual net income and subtract 25% of the payee's annual net income. The result is the guideline annual maintenance amount, subject to the 40% combined income cap.
Illinois uses a two-part statutory maintenance formula: (33.33% × payor's net income) − (25% × payee's net income). This applies when the spouses' combined gross income is below $500,000. Above that threshold, courts apply a broader discretionary analysis without being bound by this formula.
Net income for Illinois maintenance purposes is income after deducting federal and state income taxes, Social Security and Medicare taxes, and other mandatory payroll deductions. It is not gross salary. Courts and attorneys often prepare detailed net income calculations using pay stubs, tax returns, and applicable deductions.
Yes. After applying the formula, courts check whether the payee's total income — their own net income plus the maintenance award — would exceed 40% of both spouses' combined net income. If it would, the maintenance amount is reduced to bring the payee's total to exactly 40% of combined net income.
Guideline duration is calculated by multiplying the length of the marriage by a statutory multiplier. For example, a 10-year marriage uses a 0.40 multiplier, producing a guideline duration of 4 years. Multipliers range from 0.20 for marriages under 5 years up to 0.80 for marriages of 19–20 years. For marriages of 20 or more years, the court may award maintenance for a period equal to the length of the marriage or indefinite maintenance.
For marriages of 20 years or longer, 750 ILCS 5/504 gives Illinois courts the discretion to order permanent or indefinite maintenance. Courts consider the age, health, employability, and financial resources of both spouses, as well as all other statutory factors, before making that determination. It is not automatic — the circumstances of the specific case matter.
Maintenance is support paid from one spouse to the other to address post-divorce economic disparity. Child support is separate court-ordered support paid for the benefit of the children, calculated under a different Illinois statute (750 ILCS 5/505) using a shared-income model based on parenting time and each parent's income. The two obligations are calculated independently.
Yes. Either party can petition an Illinois family court to modify maintenance if there has been a substantial change in circumstances — such as a significant change in either spouse's income, the payee spouse remarrying, or the payee cohabitating with a new partner on a resident, conjugal basis. The terms of the original divorce agreement may also specify whether and how modification is permitted.
Common deductions used to arrive at net income include federal income tax, Illinois state income tax, Social Security tax (6.2%), Medicare tax (1.45%), mandatory retirement contributions, and health insurance premiums paid through payroll. Voluntary deductions, such as contributions to a 401(k) above any mandatory amount, may or may not be included depending on how the court analyzes the specific case.
Even when the statutory formula applies, Illinois judges may deviate from the guideline amount or duration after weighing the full list of factors in 750 ILCS 5/504(a). These factors include the standard of living during the marriage, each spouse's age and health, contributions to the other's career or education, and whether a spouse left the workforce to care for children. The formula is a starting point; the judge's final order reflects the complete factual picture of the marriage and each spouse's circumstances.
Official Source & Regulation References
This calculator applies the statutory maintenance formula established under 750 ILCS 5/504 — the Illinois Marriage and Dissolution of Marriage Act, Section 504. The formula, duration multipliers, and 40% cap are codified directly in this statute.
Illinois courts administer maintenance through the circuit courts of each county. The Illinois Courts system (illinoiscourts.gov) provides access to local court rules and self-help resources. The Illinois State Bar Association (isba.org) can assist in locating a licensed family law attorney familiar with local Illinois family court practices.
All formula values and duration multipliers referenced in this calculator reflect the statute as of the date of publication. Illinois law can change; verify the current version of 750 ILCS 5/504 through the Illinois General Assembly website (ilga.gov) before relying on these figures for any legal proceeding.
Last Update: June 2026