How child support is calculated in the US (2026)

Every state turns a family’s finances into a child support figure with a formula written into its statutes or court rules. The formulas share a purpose: give judges, agencies and parents a consistent starting number. They don’t share a method. The same two paychecks can produce a noticeably different guideline amount on either side of a state line, and the reasons are mostly mechanical rather than mysterious.

This guide explains where the formulas come from, the families they fall into, what every worksheet asks for, and why the results differ. For your own numbers, the child support calculator runs each state’s current rules.

Why every state has a formula

Child support guidelines are a federal requirement. Under 42 U.S.C. § 667, each state must set guidelines for child support awards, by statute or by judicial or administrative rule, and review them at least once every 4 years. The same section makes the guideline result a rebuttable presumption: it is treated as the correct amount unless a written finding, or a specific finding on the record, says that applying the guidelines would be unjust or inappropriate in that case.

The federal regulation that fills in the detail, 45 CFR 302.56, sets a floor for what guidelines must contain. They must take into account all of the noncustodial parent’s earnings and income. They must include a low-income adjustment, such as a self-support reserve, for parents with a limited ability to pay. If they allow income to be imputed, they must weigh the parent’s actual circumstances first. And they may not treat incarceration as voluntary unemployment. Within those limits, each state chooses its own approach, which is why there is no single national formula.

The model families

Most guidelines belong to one of a few families. Among the jurisdictions this site covers, they divide like this.

Income shares. 41 of the jurisdictions covered here use it: Alabama, Arizona, Arkansas, California, Colorado, Connecticut, District of Columbia, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia and Wyoming. The schedule estimates what the parents would spend on the children if they all lived in one household, based on studies of family spending, and divides that amount between the parents by their share of combined income. The parent the children live with mostly is assumed to spend their share directly; the other parent pays theirs as child support.

Percentage of income. 7 of the jurisdictions covered here use it: Alaska, Mississippi, Nevada, New York, North Dakota, Texas and Wisconsin. Support is a set percentage of income that rises with the number of children. Some versions apply the percentage to the paying parent’s income alone; others apply it to the parents’ combined income and then divide the result.

Melson. Among the jurisdictions covered here, the Melson formula is used by Delaware, Hawaii and Montana. It works in layers. Each parent keeps a self-support amount, the children’s primary needs are covered next, and a standard of living adjustment then shares part of the remaining income with the children.

Labels hide a lot of variety. Two income shares states can use different schedules, start from different definitions of income and treat shared parenting time in completely different ways. The comparison in income shares vs percentage of income vs Melson walks through each family with computed numbers.

What every worksheet asks for

Whatever the model, the worksheets ask for the same handful of facts.

Each parent’s income. Among the states covered here, 31 start from gross income and 20 start from a defined net income. What counts is broader than wages: see what counts as income. If you are paid hourly or every two weeks, the income converter gives the monthly and yearly figures worksheets use.

The number of children in this case. Child support for one child compares the starting amount in every state. Amounts rise with each extra child, but not in proportion, as child support for multiple children shows.

Parenting time, usually counted in overnights a year. Many states reduce support once the paying parent’s time passes a threshold; others use a sliding formula or no adjustment at all. The parenting time calculator counts overnights from a schedule, and the parenting time guide compares the rules.

Health insurance and child care. Most worksheets add the children’s insurance premium and work-related child care to the basic amount and split them by income, or credit the parent who pays them.

Other children and earlier orders. Support already paid for children from another relationship, and children living in a parent’s home, often reduce the income used for this case.

Low- and high-income rules. A self-support reserve or minimum order applies at the bottom of the income range; at the top, schedules end and courts take over.

Why the same family gets different amounts

Take one family. Parent A earns $60,000 a year and Parent B earns $40,000. They have two children who live mainly with Parent B, and Parent A has them about one night a week.

In Texas, the guideline amount is $1,050. Texas sets child support as a percentage of the paying parent's monthly net resources: 20% for one child, rising to 40% for five or more children. The other parent's income doesn't change the guideline amount. Here Parent A’s net resources come to $4,199 a month, and the two-child percentage of 25% is applied to that.

In North Carolina, the guideline amount is $1,056. North Carolina uses the income shares model: the schedule gives the support for the parents' combined monthly gross income, and each parent is responsible for their share. The parents’ combined gross income of $8,333 a month gives a schedule amount of $1,760, and Parent A’s 60% share of income sets Parent A’s part.

Now raise Parent B’s income to $80,000. The Texas figure is $1,050, because the percentage looks only at the paying parent. The North Carolina figure becomes $917, because Parent A’s share of combined income falls.

Beyond the model itself, the differences come from a few places:

• The schedule. Each state builds its table from the economic studies it chooses on what families spend on children, and updates it on its own timetable.
• Gross or net. Applying a percentage to net income gives a different result from a gross-income schedule, even when the headline rates look similar.
• Parenting time. A family just under one state’s threshold may get no adjustment, while the same parenting schedule earns a reduction elsewhere.
• Add-ons and deductions. Insurance, child care, other children and prior orders are handled differently in each worksheet.
• Low-income protection. Self-support reserves and minimum orders vary widely and matter most when one income is small.

Each state page shows the rules that state uses and a computed example, with a link to the official worksheet or calculator.

Using the guideline amount

The guideline amount is an estimate of what the formula produces, not a prediction of an order. Courts can deviate from the guidelines, parents can agree to a different figure (which is usually checked against the guideline amount), and the facts a court accepts, such as income or overnights, can differ from the figures entered in a calculator.

Used well, the guideline amount is a reference point. It shows what the formula produces for a given set of facts, which inputs move the result most, and what to ask about. When the facts are disputed, or a parent’s income is irregular, the state’s child support agency or a family law attorney can say how the guidelines apply in that case.