How Is Child Support Calculated? A State-by-State Guide

If you are navigating a divorce or separation and have children, one of the most pressing questions you will face is: how much child support will I pay or receive? The answer depends heavily on where you live, because every state in the United States uses its own formula. While federal guidelines require all states to have a child support calculation method, the specifics vary enormously. In this guide we will break down the three major models used across the country, walk through the key factors that affect your obligation, and provide state-specific examples so you can estimate your own situation.

The Three Major Calculation Models

Across the 50 states (plus Washington D.C.), child support is determined using one of three broad approaches. Understanding which model your state uses is the first step toward estimating your payment.

1. Income Shares Model

The Income Shares Model is by far the most common approach, used by roughly 40 states including California, New York, Florida, and Illinois. The core idea is straightforward: both parents' incomes are combined to figure out how much the household would have spent on the child if the family had stayed together. That total child-rearing cost is then split proportionally based on each parent's share of the combined income.

For example, if Parent A earns $6,000 per month and Parent B earns $4,000, the combined income is $10,000. Parent A contributes 60% and Parent B contributes 40%. If the state guidelines say that a household earning $10,000/month should spend $1,500 on one child, Parent A would be responsible for $900 (60%) and Parent B for $600 (40%). The non-custodial parent then pays their share to the custodial parent.

The Income Shares Model is designed to ensure that children receive the same proportion of parental income they would have received if the parents lived together.

2. Percentage of Income Model

A smaller group of states, including Texas, Wisconsin, Mississippi, and North Dakota, use the Percentage of Income Model. This approach is simpler: it looks only at the non-custodial parent's income and applies a flat percentage based on the number of children.

In Texas, for instance, the guidelines call for 20% of the non-custodial parent's net resources for one child, 25% for two children, 30% for three, 35% for four, 40% for five, and “not less than” the five-child amount for six or more. If a non-custodial parent in Texas has a net monthly income of $5,000 and there is one child, the guideline amount would be $1,000/month.

There are two sub-variants of this model. The flat percentage version (used by Texas) applies the same rate regardless of income level, while the varying percentage version adjusts the rate based on income brackets.

3. Melson Formula

Only three states use the Melson Formula: Delaware, Hawaii, and Montana. This is the most complex model. It starts similarly to the Income Shares Model by considering both parents' incomes, but it adds a critical first step: ensuring each parent can meet their own basic needs before any support obligation is calculated.

The Melson Formula reserves a “self-support allowance” for each parent, deducts that from their income, and then applies the child support calculation to the remaining amount. If there is additional income beyond basic child support needs, the formula also includes a “standard of living adjustment” (SOLA) that gives children a share of the surplus.

Key Factors That Affect Child Support

Regardless of which model your state uses, several common factors influence the final number. Courts and child support agencies consider all of the following when calculating your obligation.

Gross and Net Income

Your income is the single largest factor. Most states consider gross income from all sources: wages, salaries, bonuses, commissions, self-employment income, rental income, dividends, Social Security benefits, and sometimes even imputed income (what you could earn if the court believes you are voluntarily underemployed). Some states then convert gross to net by subtracting taxes and mandatory deductions.

Custody Arrangement and Parenting Time

How much time each parent spends with the child directly impacts the calculation. In most Income Shares states, the parent with fewer overnights (the non-custodial parent) pays support to the custodial parent. However, many states now offer a shared custody adjustment when the non-custodial parent has the child for a significant number of overnights (often more than 90-110 nights per year). In these cases, the support amount may be reduced because the non-custodial parent is directly covering more of the child's daily expenses.

Healthcare and Insurance Costs

The cost of health insurance premiums for the child is almost always factored in. Courts typically order one parent to maintain health coverage, and the premium cost attributable to the child is added to the base support obligation and shared proportionally. Unreimbursed medical expenses (co-pays, deductibles, prescriptions) are usually split between the parents as well, often in proportion to income.

Daycare and Childcare Expenses

Work-related childcare costs are a major add-on in virtually every state. If a parent needs to pay for daycare, after-school care, or a nanny in order to work, those costs are typically added to the base support calculation and divided between the parents. Some states also consider summer camp costs and extracurricular activity fees.

Number of Children

More children means a higher total obligation, though the per-child amount typically decreases with each additional child due to economies of scale. State guidelines provide specific schedules or multipliers for families with multiple children.

Other Factors

• Pre-existing child support orders for other children
• Special needs of the child (medical, educational, therapeutic)
• The child's own income or assets (rare, but considered for older teens)
• Standard of living during the marriage
• Tax filing status and deductions

State-by-State Examples

To illustrate how dramatically results can differ, let us consider the same hypothetical family across four states. Assume: Parent A (non-custodial) earns $6,000/month gross, Parent B (custodial) earns $3,000/month gross, one child, standard custody arrangement (every other weekend), and no extraordinary expenses.

California (Income Shares)

California uses a complex algebraic formula codified in Family Code Section 4055. The formula is: CS = K[HN - (H%)(TN)], where K is a factor based on the higher earner's time with the child, HN is the high earner's net monthly disposable income, H% is the high earner's approximate share of time with the child, and TN is the total net disposable income of both parents. For our example, the guideline amount would typically fall between $1,100 and $1,300/month, depending on exact deductions and the timeshare percentage.

Texas (Percentage of Income)

Texas uses the simpler flat-percentage model. For one child, the guideline is 20% of the non-custodial parent's net resources. If Parent A's net monthly resources come to approximately $4,800 after taxes and deductions, the guideline child support would be about $960/month. Texas does not consider the custodial parent's income in the basic calculation, though a court can deviate from guidelines in certain circumstances.

New York (Income Shares)

New York's formula combines both parents' incomes up to a statutory cap (currently $163,000/year combined, adjusted periodically). The combined parental income is multiplied by a percentage based on the number of children: 17% for one child, 25% for two, 29% for three, 31% for four, and at least 35% for five or more. That amount is then prorated based on each parent's share of combined income. For our example, the combined annual income is $108,000. Seventeen percent yields $18,360/year or $1,530/month total. Parent A's share (67%) would be about $1,025/month.

Florida (Income Shares)

Florida uses the Income Shares Model with a detailed guideline schedule. The combined monthly net income of $9,000 for one child corresponds to a basic support need of roughly $1,210/month per the Florida guidelines schedule. Parent A's proportional share (67%) would be approximately $811/month. Florida also adds healthcare premiums and daycare costs on top of this base amount, divided proportionally.

As you can see, the same family could pay anywhere from $811 to $1,300 per month depending on the state. This is why using a state-specific calculator is essential.

How to Estimate Your Child Support

While understanding the models and factors is important, the fastest way to get an estimate is to use a calculator that incorporates your state's specific guidelines. CalcViral's child support calculator lets you select your state, enter both parents' incomes, specify custody arrangements, and add healthcare and childcare costs to get a guideline estimate in seconds.

Can Child Support Be Modified?

Yes. Child support orders are not permanent. Either parent can petition the court for a modification if there is a substantial change in circumstances. Common reasons include a significant change in either parent's income (job loss, promotion, disability), a change in the custody arrangement, changes in the child's needs (medical conditions, educational requirements), or the child reaching the age of emancipation.

Most states require a change of at least 10-20% from the current order before they will modify it. The process typically involves filing a motion with the court, providing updated financial information, and either reaching an agreement or having a judge decide.

Tips for Navigating Child Support

• Document everything. Keep records of all income, expenses, and payments. Courts rely heavily on financial documentation.
• Use your state's worksheet. Most states publish official child support worksheets. Filling one out before court gives you a baseline expectation.
• Consider mediation. Many disputes about child support can be resolved through mediation, which is faster and less expensive than litigation.
• Consult a family law attorney. While calculators provide useful estimates, a lawyer can advise on deviations, imputed income issues, and complex situations like self-employment or interstate cases.
• Stay current on payments. Falling behind on child support can lead to wage garnishment, license suspension, and even contempt of court charges.

Final Thoughts

Child support exists to ensure that children maintain a reasonable standard of living after their parents separate. While the calculations can seem daunting, understanding your state's model and the factors involved puts you in a much better position to plan ahead. Use our free child support calculator to run the numbers for your specific situation, and always consult a family law professional for advice tailored to your case.