Every state has child support guidelines, but the formulas are not the same. Most use the Income Shares Model, a handful use the Percentage of Income Model, and three states use the Melson Formula. Knowing which model applies to you is the first step in understanding what your support order will look like.
This guide walks through each model with worked examples, explains what counts as income, and covers the adjustments most likely to change the final number. For a state-specific estimate, our Child Support Calculator implements every state's current guideline.
The three formula models
Income Shares Model. Used in 41 states. The model assumes children should receive the same proportion of parental income they would have received if the parents lived together. The formula starts with combined parental income, looks up a "basic obligation" on a state schedule, and divides that obligation between parents in proportion to their incomes. States using this model include California, Florida, New York, Pennsylvania, Illinois, Ohio, Georgia, North Carolina, New Jersey, Virginia, Michigan, Massachusetts, Arizona, Washington, Indiana, Tennessee, Missouri, Maryland, Wisconsin, Colorado, Minnesota, South Carolina, Alabama, Louisiana, Kentucky, Oregon, Oklahoma, Connecticut, Iowa, Mississippi, Arkansas, Kansas, Utah, Nevada, New Mexico, Nebraska, Idaho, West Virginia, Hawaii, New Hampshire, Maine, Rhode Island, Vermont, South Dakota, and Wyoming.
Percentage of Income Model. Used in Texas, Mississippi (for low-income cases), North Dakota, and Alaska in modified forms. The non-custodial parent pays a flat percentage of net income based on the number of children. The custodial parent's income is generally not part of the calculation.
Melson Formula. Used in Delaware, Hawaii, and Montana. A more complex variant of Income Shares that includes a "self-support reserve" allowing each parent to keep a baseline amount of income before any support obligation is calculated.
Income Shares example: $5,000 combined income, two children, 70/30 custody
Assume the parents have a combined gross monthly income of $5,000 (Parent A: $3,500, Parent B: $1,500). Two children. Parent A has 30% parenting time; Parent B has 70%. We will use a representative state schedule (the actual schedule is set by each state).
Step 1: Find the basic child support obligation. Look up $5,000 combined income with two children on the state schedule. A typical schedule shows about $1,150 per month.
Step 2: Pro-rate the obligation by income share. Parent A earns 70% of combined income (3,500 / 5,000). Parent A's share of the obligation: 70% of $1,150 = $805.
Step 3: Apply parenting-time adjustments. Parent A has 30% parenting time, which in most states does not trigger a shared-custody adjustment (the threshold is typically 35% or higher). Parent A pays the full $805 to Parent B as the custodial parent.
Step 4: Add proportional shares of work-related childcare and health insurance. If the children's health insurance costs $250 per month and Parent B pays it, Parent A's share of that is 70%, or $175. Parent A's total order: $805 + $175 = $980 per month.
That is the basic structure. Each state schedule produces slightly different basic obligation numbers, and each state's adjustments differ in detail, but the four-step structure is the same.
Percentage of Income example: Texas
Texas applies fixed percentages to the obligor's "net resources" (gross income minus federal income tax, Social Security, Medicare, state income tax, and the cost of the children's health insurance).
| Number of children | Percentage of net resources | |---|---| | 1 child | 20% | | 2 children | 25% | | 3 children | 30% | | 4 children | 35% | | 5 children | 40% | | 6+ children | At least 40% |
Example: Obligor has gross income of $6,000 per month. After federal taxes, Social Security, and Medicare, net resources are about $4,800. With two children, the order is 25% of $4,800 = $1,200 per month.
Texas caps the percentage application at the first $9,200 of monthly net resources (the cap is updated periodically by the Texas Family Code). Above the cap, the court has discretion.
Melson Formula example: Delaware
The Melson Formula, used in Delaware, calculates support in three layers:
- Self-support reserve. Each parent keeps a baseline amount of income to meet their own minimum needs (about $1,000 to $1,200 per month, adjusted for inflation).
- Primary support obligation. Above the reserve, each parent contributes proportionally to a basic child support amount based on the number of children.
- Standard of living adjustment (SOLA). Above the primary obligation, additional income produces additional support designed to give the children a share of the parents' improved standard of living.
Example: Parent A earns $4,500/month, Parent B earns $2,500/month, two children with Parent B.
After subtracting Parent A's self-support reserve ($1,100), Parent A has $3,400 of available income. After Parent B's reserve, Parent B has $1,400.
The state primary obligation table shows about $850 for two children. Parent A's share is $3,400 / ($3,400 + $1,400) = about 71%, so Parent A's primary obligation is $603.
The SOLA adds a percentage (typically 18% for two children) of Parent A's remaining income above the primary obligation. That percentage produces about $500 of additional support.
Parent A's total order: $603 + $500 = about $1,103 per month.
The full Melson calculation is more involved than this summary, and Delaware Family Court has worksheets that walk through each step. The result is generally higher than a simple Income Shares calculation, particularly for higher-income obligors.
What counts as income
Almost everything counts. State guidelines define income broadly:
- Wages and salary, including bonuses, commissions, and overtime.
- Self-employment income, after legitimate business deductions. Courts scrutinize self-employment deductions closely because they can be used to mask income.
- Investment income. Dividends, interest, capital gains.
- Rental income. Net of mortgage interest, taxes, and operating expenses.
- Retirement income. Pension payments, IRA withdrawals, Social Security retirement.
- Disability and workers' compensation.
- Unemployment benefits.
Many states also include in-kind benefits (employer-provided housing, company cars) at fair market value.
Imputed income. If a parent is voluntarily unemployed or underemployed, courts can impute income based on what the parent could reasonably earn. The standard varies: some states require a finding of bad faith; others impute based on earning capacity regardless of motive. A parent who quits a job during a divorce should expect imputed income unless there is a documented health, caregiving, or education reason.
How parenting time affects child support
Almost all Income Shares states have a "shared custody" adjustment that reduces the support order when both parents have substantial time with the children. The threshold varies:
- Most common threshold: 40% of overnight time. Below 40%, the standard formula applies. Above 40%, the order is calculated using a shared-custody worksheet that gives both parents credit for the costs they incur during their parenting time.
- Some states use 35% or 30% as the threshold. Colorado uses 92 overnights per year (about 25%).
- A few states do not adjust for parenting time at all below 50/50. Texas, for example, does not reduce its percentage for high non-custodial parenting time unless it is essentially equal time.
A 50/50 schedule does not always produce zero support. If one parent earns substantially more, the higher-earning parent typically still pays the lower-earning parent something to equalize the children's standard of living between households.
Health insurance and childcare credits
Two adjustments come up in almost every case:
Health insurance for the children. The cost of the children's portion of the parent's health insurance premium is added to the basic obligation, then split proportionally. Whichever parent pays the premium gets credit for the other parent's share.
Work-related childcare. Daycare, after-school care, and summer camps that allow parents to work are added to the basic obligation and split proportionally. Most states do not include nanny costs above the cost of equivalent daycare unless the children have special needs.
These two adjustments can change the final order by hundreds of dollars per month, especially when childcare is significant.
Income caps and high earners
Most state guidelines stop applying mechanically above a certain income level:
- Texas: Caps the percentage at the first $9,200 of monthly net resources.
- California: No formal cap, but DissoMaster (the standard guideline software) is rarely used above about $25,000 in monthly net income.
- New York: Cap at $183,000 of combined parental income (updated periodically). Above the cap, judges may continue applying the formula or apply discretion.
- Pennsylvania: Schedule extends to $30,000 combined monthly income; above that, judges have discretion.
Above the cap, courts typically consider the child's "reasonable needs" and the lifestyle the children would have enjoyed but for the divorce. High-earner cases often involve specific budgets for school, activities, and travel, which can produce significantly higher orders than a mechanical formula extension would.
How to modify child support
Child support is modifiable when there is a "substantial change in circumstances." Common triggers:
- A change in either parent's income of 15% or more, sustained for at least three to six months.
- A change in custody or parenting time that crosses a guideline threshold.
- A change in the children's needs (medical, educational, special needs).
- Emancipation of one of the children covered by the order.
- A new child for either parent (some states adjust for after-born children, others do not).
The modification process is initiated in the same court that issued the original order. If both parents agree, the modification can usually be done by stipulation in a few weeks. Contested modifications follow the same procedures as the original case.
Modifications generally apply only from the date the motion is filed forward, not retroactively. If your circumstances change, file promptly.
Run your numbers
The state-specific math gets complicated quickly. Our Child Support Calculator handles your state's formula, parenting-time adjustments, health insurance, and childcare automatically. For a full picture of total divorce costs, run it alongside the Divorce Cost Estimator.
This estimate is for planning purposes only and does not constitute legal or financial advice. Consult a licensed family law attorney in your state for guidance specific to your situation.