Child support is designed to ensure that children receive the same financial support from their parents after a separation or divorce as they would if the parents lived in a single household. While the moral and legal obligation is clear, the actual calculations used to determine child support payments are highly complex and vary significantly depending on where you live.
Every state in the United States uses its own guidelines and mathematical formulas to establish support obligations. This guide breaks down the three primary child support models used in the US, explains what counts as income, details how custody arrangements affect payments, and outlines how to use our child support calculator to estimate your monthly budget. Our Child Support Calculator estimates monthly payments for all 50 states using the correct legal model for each.
The Three Main Child Support Models in the United States
States use one of three main frameworks to calculate child support. The model your state uses dictates which numbers you need to enter into the formula.
1. The Income Shares Model (Used by 38+ States)
The Income Shares Model is based on the principle that the child should receive the same proportion of parental income that they would have received if the parents were still together.
How it works:
- The court determines the gross or net income of both parents and adds them together.
- It references a state-specific table to find the “basic support obligation” for that combined income level and number of children.
- The total obligation is divided proportionally between the parents based on their share of the combined income.
- The non-custodial parent pays their share to the custodial parent.
States using this model include California, Florida, New York, Colorado, Ohio, and North Carolina.
2. The Percentage of Income Model (Used by 9+ States)
The Percentage of Income Model is simpler: it looks only at the income of the non-custodial parent (the parent who does not have primary custody).
How it works:
- The court determines the net or gross income of the non-custodial parent.
- It applies a flat percentage based on the number of children being supported.
- The custodial parent’s income is generally ignored in this basic calculation.
States using this model include Texas, Illinois, Wisconsin, Mississippi, and Alaska.
Typical Percentage Rates (e.g., Texas):
- 1 child: 20% of net resources
- 2 children: 25% of net resources
- 3 children: 30% of net resources
- 4 children: 35% of net resources
- 5+ children: 40% of net resources
3. The Melson Formula (Used by 3 States)
The Melson Formula is a highly complex variation of the Income Shares Model. It is designed to ensure that both parents can meet their own basic needs before support is calculated, but also allows children to share in any surplus income.
How it works:
- Calculate a self-support allowance for each parent (basic survival cost).
- Calculate the basic child support needs.
- If parents have income left over after meeting self-support and basic child support, a secondary “standard of living adjustment” (SOLA) percentage is applied to the remaining surplus income.
States using this model are Delaware, Hawaii, and Montana.
What Counts as Income for Child Support Calculations?
When courts calculate child support, they start with a parent’s “gross income.” This definition is typically much broader than taxable income under the IRS code.
Income sources almost always included:
- Hourly wages, salaries, and tips
- Self-employment or business partnership income
- Commissions, bonuses, and overtime pay
- Interest, dividends, and capital gains from investments
- Pension, retirement, and Social Security benefits
- Unemployment compensation and workers’ compensation benefits
- Alimony or spousal support received from a different relationship
What is generally EXCLUDED from gross income:
- Supplemental Security Income (SSI) and other public assistance benefits (TANF, food stamps)
- Income of a new spouse or domestic partner (though their contribution to household expenses can sometimes be reviewed in special circumstances)
Imputed Income: Voluntary Underemployment
If a parent quits a high-paying job or refuses to work to lower their child support obligation, the court can impute income. This means the court calculates support based on what the parent should be earning, given their work history, education, and local job market conditions, rather than their actual $0 or low wage.
How Custody & Parenting Time Adjustments Work
The custody arrangement is one of the most critical factors in child support calculations.
- Sole Custody: The non-custodial parent pays the full calculated support obligation to the custodial parent.
- Shared / Joint Custody: If the non-custodial parent has the children for a significant portion of the year (usually at least 20% to 35% of overnights, depending on the state), the state applies a parenting time adjustment. This reduces the child support payment to reflect the direct expenses the parent incurs while the children are in their care (food, utilities, entertainment).
- Equal 50/50 Custody: Having equal custody does not mean no child support is paid. If one parent earns $150,000/year and the other earns $40,000/year, the higher-earning parent will still pay support to ensure the child enjoys a similar standard of living in both households.
How to Use Our Child Support Calculator
Our free Child Support Calculator simplifies state-specific calculations. To get a realistic estimate:
- Select Your State: This loads the correct legal model (Income Shares, Percentage of Income, or Melson) and state tax deduction formulas.
- Enter Incomes: Enter gross monthly income or net resources as prompted by your state selection.
- Specify Child Count: Enter the number of children covered by the support order.
- Enter Parenting Overnights: Input the number of annual overnights the children spend with each parent to calculate joint-custody discounts.
- Add Extra Expenses: Enter monthly health insurance premiums, child care costs, and extraordinary medical expenses, which are typically shared proportionally in addition to basic support.
Disclaimer: Child support calculations are subject to judicial discretion. Courts can depart or “deviate” from the standard guideline calculations if strict application would be unjust, inappropriate, or not in the best interest of the child. Use this tool as an estimate, and consult with a licensed family law attorney in your jurisdiction for binding legal advice.