How Much Is Child Support and How Is It Calculated?

The average child support payment in the United States is about $670 per month, according to the most recent Census Bureau data, but individual orders run from under $100 to several thousand dollars.¹ How much child support you’ll pay or receive depends on three things: the formula your state uses, the income both parents bring to that formula, and the amount of time the child spends with each parent. Federal law requires states to follow published guidelines, and a judge can deviate from the guideline number only by writing out why the standard result would be inappropriate in your case.²

The Formula Your State Uses

About 41 states use the income shares model. Courts estimate what both parents would have spent on the child if they still lived together, then split that cost in proportion to each parent’s earnings. Both incomes are combined, the total is matched to a table in the state guidelines showing the expected cost of raising a child at that income level, and each parent’s share tracks their percentage of the combined income.³ If one parent earns 65% of the combined income, that parent is responsible for 65% of the child-related obligation.

Six states use a percentage-of-income model, which looks only at the noncustodial parent’s income and applies a set percentage for each child. Some use a flat percentage at every income level; others use a percentage that decreases as income rises. The custodial parent’s earnings don’t enter the equation because the model assumes that parent is already spending directly on the child through housing, meals, and daily care.³ The remaining states use hybrid approaches that blend elements of both.

Whichever model your state follows, the guideline produces a presumptive amount. That number is the starting point, and in most cases, it’s also the ending point.

What Counts as Income

Child support formulas start with gross income, which covers far more than a base salary. Overtime, commissions, bonuses, tips, rental income, investment returns, and even recurring gifts can all count. Courts review tax returns, W-2s or 1099s, and several months of pay stubs. When income fluctuates because of seasonal or commission-based work, the court will usually average earnings over a longer window rather than rely on a single recent check.

Certain deductions come off the top before the formula runs: federal and state income taxes, Social Security and Medicare withholdings, mandatory retirement contributions, union dues, and existing support obligations for other children. Health insurance premiums paid for the child specifically are also pulled out, since that money is already going toward the child’s needs. What remains is the net income, or “net resources” in some states, that feeds the guideline calculation.

Self-Employment Income

Self-employed parents can’t simply hand the court a Schedule C and call the bottom line their income. Courts start with gross business receipts and allow deductions only for expenses genuinely necessary to run the business, such as inventory, employee wages, business insurance, and commercial rent. Non-cash write-offs like depreciation are commonly added back, because they don’t represent money actually leaving your pocket. Personal expenses routed through the business get the same treatment: a vehicle used mostly for personal driving or a “home office” that’s really a spare bedroom won’t reduce the income the court uses. Perks like a company car, employer-paid phone, or housing allowance may also be counted as income because they reduce living expenses the parent would otherwise pay out of pocket.

Imputed Income

A parent can’t dodge support by quitting a job or deliberately working part-time. When a court finds that a parent is voluntarily unemployed or underemployed in bad faith, it will calculate support based on what that parent could be earning rather than actual take-home pay. Judges consider education, work history, professional skills, and job availability in the local area. Common triggers include quitting without good cause, taking early retirement, turning down promotions, or cutting hours to pursue hobbies. Involuntary situations, like a genuine layoff or a documented disability, usually spare the parent from imputed income, provided they can show a real effort to find new work.

Add-On Expenses Beyond the Base Amount

The guideline number covers everyday costs: food, clothing, shelter, basic school supplies. Several categories sit on top of the base obligation and get divided between parents separately, usually in proportion to income.

Work-related childcare, including daycare, after-school programs, and summer care, is typically added to the base obligation and split by income share. When the child moves from daycare to school and those costs drop, either parent can request a modification.
Unreimbursed medical expenses — copays, deductibles, orthodontia, therapy, prescriptions — are split between parents, most often using the same income-based percentage that applies to the base obligation.
Health insurance premiums must be addressed in every child support order under federal law. The cost of adding the child to a parent’s employer plan is usually either factored into the support calculation or ordered separately.²
Private school tuition, tutoring, sports fees, and similar costs are not automatically included in most states. Courts will consider them if the child was already enrolled before the separation, if both parents agreed to the expense, or if the child has a demonstrated special need. Without one of those factors, judges rarely force a parent to pay above-guideline amounts for activities the other parent chose on their own.

How Custody Time Changes the Number

The more overnights a child spends with each parent, the more the support calculation shifts. When one parent has primary custody and the other has standard visitation, the formula runs straightforwardly. Once the noncustodial parent’s time crosses a threshold that varies by state and falls somewhere between 80 and 146 overnights per year, a shared-parenting formula kicks in and typically lowers the support amount. The reasoning is simple: a parent with the child 40% of the time or more is already covering a significant share of daily expenses directly.

In roughly equal custody arrangements, many states use a cross-credit calculation. Each parent’s hypothetical obligation to the other is computed, and the difference becomes the payment. The higher earner usually still pays something, because the goal is a comparable standard of living in both homes. Parenting schedules are documented carefully, and courts watch closely for parents who exaggerate overnights to lower a support order.

Changing the Amount Later

A child support order isn’t permanent. Either parent can ask the court to adjust the amount when circumstances change significantly. Most states require a change that is substantial, involuntary, and expected to last. Qualifying events include a job loss through no fault of your own, a serious illness or disability, a large income increase for the paying parent, a change in custody, or a child aging out of daycare. Federal law also requires states to review orders in cases involving public assistance at least every three years, even without a request from either parent.⁴

One rule catches many paying parents off guard. Modifications cannot be applied retroactively. Under the federal Bradley Amendment, every support payment becomes a judgment the moment it comes due, and no court can forgive or reduce payments that accrued before the modification petition was filed.⁴ If your income drops in January but you don’t file until June, you still owe the original amount for those five months. Filing promptly when circumstances change is the single most important thing a paying parent can do to protect themselves.

When the Obligation Ends

In most states, child support terminates when the child turns 18 or graduates from high school, whichever comes later. A handful of states set the cutoff at 19, and a small number extend it to 21.⁵ Support can also end earlier if a minor is legally emancipated through marriage, active-duty military service, or a court finding that the child is self-supporting and living independently.

Two situations extend support past the age of majority. Many states allow courts to order continued support, or a separate contribution toward college expenses, for a child enrolled in postsecondary education. Parents can also commit to college support voluntarily in a separation agreement, and courts will enforce that commitment. The second situation involves children with physical or mental disabilities who cannot support themselves as adults. Most states require parents to continue contributing, with the amount set either by the standard guidelines or by the child’s documented needs weighed against the parents’ ability to pay.⁵

Support does not end automatically on the child’s birthday. The paying parent must file a petition and obtain a court order formally terminating the obligation. Until that order is entered, payments keep accruing, and under the Bradley Amendment, accrued payments cannot be wiped out after the fact.

1
U.S. Census Bureau. Child Support Received: 2023
2
Administration for Children and Families. How Is the Amount of My Child Support Order Set?
3
National Conference of State Legislatures. Child Support Guideline Models
4
Administration for Children and Families. Essentials for Attorneys – Chapter Twelve: Modification of Child Support Obligations
5
National Conference of State Legislatures. Termination of Child Support