Child Support Calculator: How Payments Work by State

Child Support in 2026: What to Expect

The short answer: the U.S. Census Bureau pegs the average monthly child support payment at roughly $480, but that number hides enormous variation. Payments start as low as $100/month for low-income parents with one child and run past $5,000/month for high-income families. Your state's guideline model — Income Shares, Percentage of Income, or Melson — drives the bulk of that variation, and judges deviate from guidelines in fewer than 10% of cases.

Every state has child support guidelines that establish a presumptive support amount based on a mathematical formula. Courts are required to calculate support using the guidelines, and the resulting amount is presumed to be correct. A judge can deviate from the guidelines only if specific findings justify it — such as extraordinary medical expenses, special educational needs, or a child's independent income. In practice, the guidelines determine the support amount in roughly 90% of cases.

The three calculation models used across all 50 states are the Income Shares model (used by 41 states and D.C.), the Percentage of Income model (used by 6 states), and the Melson Formula (used by 3 states). Each model approaches the calculation differently, and the resulting support amounts can vary significantly for the same income levels. Use our Child Support Estimator to calculate the estimated payment in your state based on your specific income and custody arrangement.

Child support obligations are separate from and in addition to alimony. A parent may owe both child support and spousal support, though the interaction between the two varies by state. In many states, the child support calculation is performed after alimony is determined, with the alimony payment reducing the payer's income and increasing the recipient's income for child support purposes. Our Alimony Calculator can help you model this interaction.

The Three Calculation Models Explained

The Income Shares model is by far the most common, used by 41 states including California, New York, Florida, Texas (for its basic formula), Illinois, Ohio, and Pennsylvania. It is based on the principle that a child should receive the same proportion of parental income as they would have if the parents lived together. The model combines both parents' incomes, looks up the total child support obligation from a table based on that combined income and the number of children, and then divides the obligation between the parents in proportion to their respective incomes.

For example, in an Income Shares state where Parent A earns $6,000 per month and Parent B earns $4,000 per month, the combined income is $10,000. The state's guideline table might set the total support obligation for two children at $1,800 per month. Parent A's share would be 60% ($1,080) and Parent B's share would be 40% ($720). If Parent B is the custodial parent, Parent A would pay $1,080 per month in child support, because the law assumes Parent B is already spending their share directly on the children.

The Percentage of Income model, used by Alaska, Mississippi, Nevada, North Dakota, Texas, and Wisconsin, is simpler. It calculates support as a flat percentage of the non-custodial parent's income, without considering the custodial parent's income. Texas uses the most well-known version: 20% of net income for one child, 25% for two children, 30% for three, 35% for four, and 40% for five or more. Alaska uses a similar structure: 20% for one child, 27% for two, and 33% for three. If the non-custodial parent in Texas earns $5,000 per month net, child support for two children would be $1,250 per month.

The Melson Formula, used by Delaware, Hawaii, and Montana, is the most complex model. It incorporates a self-support reserve for each parent (ensuring neither parent falls below a minimum standard of living), a primary support amount for the child, and a standard of living adjustment that allocates a portion of any remaining income to the child. The Melson Formula tends to produce higher support amounts for higher-income parents than the other models because of the standard of living component. On a combined income of $10,000 per month with two children, the Melson Formula might yield $2,000 to $2,400 per month — compared to $1,600 to $1,800 under Income Shares.

How Custody Time Affects Child Support

The custody arrangement — specifically, the percentage of overnights each parent has — directly affects the child support calculation in most states. The general principle is that the more time a parent spends with the child, the more direct expenses they incur, and the less child support they should pay (or the more they should receive). Most states have a threshold at which shared custody triggers a different calculation.

In many Income Shares states, shared custody adjustments kick in when the non-custodial parent has the child for more than 25% to 30% of overnights (roughly 92 to 110 nights per year). Above this threshold, the calculation multiplies the basic support obligation by a factor (typically 1.5) and then allocates each parent's share based on both income and time. This 'shared parenting adjustment' can reduce the non-custodial parent's payment by 20% to 50% compared to a standard calculation.

For example, in Virginia, if the non-custodial parent has the child for 100 overnights (27% of the year), the standard calculation applies. But if they have 110 overnights (30%), the shared custody formula kicks in, potentially reducing the monthly payment from $1,200 to $850 — a $350 per month difference. This creates a strong financial incentive to negotiate at least 110 overnights, which is a common negotiation point in custody agreements.

In Percentage of Income states like Texas, the shared custody adjustment is less dramatic. Texas adjusts the base percentage if the child spends at least 123 overnights (roughly 34% of the year) with the non-custodial parent, but the adjustment is modest compared to Income Shares states. In equal (50/50) custody arrangements, most states calculate each parent's obligation and then require the higher-earning parent to pay the difference. On incomes of $6,000 and $4,000 per month with 50/50 custody and two children, the net payment might be $300 to $500 per month from the higher earner to the lower earner.

Use our Child Support Estimator to model how different custody arrangements affect the payment amount in your state. Even a small change in overnights — from 120 to 130, for example — can make a meaningful difference in the calculation.

Deductions, Adjustments, and Add-Ons

The basic child support formula is only the starting point. Most states allow deductions from gross income before calculating support, and many add specific expenses on top of the base amount. Understanding these adjustments helps you estimate a more accurate payment amount.

Common deductions from income include: federal and state income taxes (using the standard deduction), Social Security and Medicare taxes (FICA), mandatory retirement contributions, union dues, health insurance premiums for the parent only, and pre-existing child support obligations for children from other relationships. In most states, voluntary retirement contributions above the mandatory amount are not deducted, and investment income, bonuses, and overtime are generally included in gross income.

Add-on expenses are costs that courts order in addition to the base support amount, typically split between the parents in proportion to their incomes. The most common add-ons include: work-related childcare costs ($800 to $2,000 per month per child in most markets), health insurance premiums for the child ($200 to $600 per month), unreimbursed medical expenses above a threshold (typically $250 per year per child), and extraordinary educational expenses such as tutoring or private school tuition. In California, add-ons for childcare and health insurance are mandatory; other states make them discretionary.

Some states also address specific expenses like travel costs for visitation (particularly relevant when parents live in different states), extracurricular activities, and summer camp. These are usually addressed case by case rather than by formula. If you expect significant add-on expenses, be sure to include them when budgeting for total child-related costs. The base child support payment alone may cover only 60% to 70% of the total financial obligation.

Self-employment income receives special treatment in most states. Courts typically examine the parent's tax returns, business records, and bank statements to determine true income, rather than relying solely on the self-reported income. Business expenses that are tax-deductible but do not actually reduce the parent's standard of living — such as personal vehicle expenses, home office deductions, and meals — may be added back to income for child support purposes. If one parent is self-employed, the child support calculation often requires additional financial analysis.

Modifying Child Support

Child support orders are not permanent. Either parent can petition the court for a modification if there has been a substantial change in circumstances. Most states define 'substantial' as a change that would alter the support amount by at least 10% to 20% from the current order, or a specific dollar amount (often $50 to $100 per month). Common grounds for modification include job loss, significant income change, change in custody arrangement, additional children in a new relationship, and changes in the child's needs.

The modification process typically begins with filing a motion with the family court, along with updated financial disclosures. Filing fees range from $50 to $300 depending on the state. If both parents agree to the modification, the process can be completed quickly — often within 30 to 60 days. If the modification is contested, it may require a hearing and take 3 to 6 months, with attorney fees of $1,500 to $5,000.

Many states offer expedited modification processes for certain situations. If the non-custodial parent is incarcerated, some states automatically review and reduce the support obligation. If either parent receives public assistance, the state child support enforcement agency may initiate a review. Several states now offer online modification tools that simplify the process for parents who agree on the changes.

One critical rule applies everywhere: child support modifications are generally not retroactive. If you lose your job in January but do not file for modification until June, you owe the full original amount for January through June. Arrears accumulate automatically, and they cannot be discharged in bankruptcy. If your circumstances change, file for modification immediately — do not wait. The court can only reduce your obligation from the date you file, not from the date your circumstances changed.

Enforcement: What Happens If a Parent Does Not Pay?

Child support enforcement is one of the most aggressive areas of family law. Federal and state governments have established powerful tools to collect unpaid support, and the consequences of non-payment are severe. According to the Office of Child Support Enforcement, approximately $33 billion in child support was collected in 2023, but another $113 billion in arrears remains outstanding.

The most common enforcement tool is income withholding (wage garnishment). Under federal law, all new child support orders must include an income withholding order that directs the non-custodial parent's employer to deduct the support amount directly from their paycheck. Up to 50% of disposable income can be garnished for child support if the payer has another family to support, and up to 65% if they do not. Income withholding accounts for approximately 70% of all child support collected.

For parents who are self-employed or whose income withholding is insufficient, states have additional tools: interception of federal and state tax reimbursements, suspension of driver's licenses and professional licenses, denial or revocation of passports (for arrears exceeding $2,500), bank account levies, liens on real and personal property, and reporting to credit bureaus. In extreme cases, non-payment of child support can result in contempt of court charges and incarceration — up to 6 months for civil contempt and longer for criminal contempt.

If you are owed child support and the other parent is not paying, contact your state's child support enforcement office. These agencies provide free services to locate non-paying parents, establish paternity, obtain and enforce support orders, and collect arrears. You can find your state's office through the federal Office of Child Support Enforcement at www.acf.hhs.gov/css. Private enforcement — such as hiring an attorney to file a contempt motion — is also an option, typically costing $1,000 to $3,000.

Until What Age Is Child Support Paid?

Child support generally ends when the child turns 18, but many states extend the obligation beyond that age under specific circumstances. Understanding your state's termination rules helps you plan long-term finances and avoid surprises.

In the majority of states, child support ends at age 18 or when the child graduates from high school, whichever comes later. If a child turns 18 in February but does not graduate until June, support continues through graduation. A few states end support at age 18 regardless of high school status, including Alabama, Alaska, and Louisiana.

A significant number of states extend child support for college-age children. In New York, child support continues until age 21 — one of the longest default durations in the country. In Indiana, support can be extended to age 21 if the child is enrolled in a postsecondary institution. In New Jersey, courts have historically required child support and college contribution until the child is 'emancipated,' which often means through completion of a four-year degree. Massachusetts allows support until age 23 if the child is enrolled in an educational program. Illinois allows courts to order both parents to contribute to college expenses, even beyond the age when basic support ends.

Child support can end earlier than the default age if the child becomes emancipated — meaning they join the military, get married, become financially self-supporting, or are legally declared an adult by a court. In most states, the parent seeking to end support must file a motion with the court; child support does not automatically terminate on a birthday. Continuing to pay until you have a court order terminating the obligation protects you from arrears.

For disabled children who cannot become self-supporting, many states allow child support to continue indefinitely — potentially for the child's entire life. If your child has a disability, discuss the long-term support obligation with your attorney and plan accordingly. Use our Child Support Estimator to model support for your specific state and circumstances, and see our child support by state guide for a complete comparison of age limits.

Using the Child Support Calculator

Our Child Support Estimator uses your state's specific guidelines to calculate an estimated monthly payment. The calculator applies the correct model — Income Shares, Percentage of Income, or Melson Formula — based on the state you select, and factors in the number of children, both parents' incomes, and the custody arrangement.

To get started, you need: the state where the child support order will be issued, both parents' gross monthly income (from all sources including wages, self-employment, investment income, and benefits), the number of children, and the custody schedule (specifically, the number of overnights per year with each parent). If you have information about childcare costs, health insurance premiums for the children, and any pre-existing support obligations, including those will improve the estimate's accuracy.

Here is what to expect for common scenarios: In Texas (Percentage of Income model), a non-custodial parent earning $5,000 per month net with two children would pay approximately $1,250 per month (25% of net income). In California (Income Shares), combined parental income of $12,000 per month with two children and a 70/30 custody split would yield approximately $1,500 to $1,800 per month from the higher-earning parent. In Florida (Income Shares), the same scenario would produce approximately $1,400 to $1,700 per month.

The calculator provides a range rather than a single number because real-world cases involve deductions, add-ons, and judicial discretion that cannot be captured in a simple tool. For the most accurate estimate, we recommend using the calculator as a starting point and then consulting with a family law attorney in your state who can account for your specific deductions and circumstances. Explore state-specific pages like Texas, California, and Florida for detailed guidance on your state's rules.