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

Why Child Support Formulas Exist

The short answer: every state has to run a formula — that's been federal law since 1988 under 42 U.S.C. § 667. Before that, two families with identical incomes could walk out of different courtrooms with wildly different orders.

Today, guidelines give you a starting number, and the 2026 formulas range from Texas's flat 20% for one child to New York's 17% CSSA cap on $193,000 of combined income. Whether your state uses income shares, straight percentage, or the Melson formula changes the math dramatically.

Before standardized guidelines, child support amounts were left entirely to judicial discretion, leading to wildly inconsistent outcomes. Two families with identical incomes and identical numbers of children might receive dramatically different orders depending on the judge assigned to their case. Today's guidelines reduce that inconsistency by using mathematical formulas that account for income, number of children, custody arrangements, and other factors.

That said, the formulas vary significantly from state to state. The three main models are the income shares model, the percentage of income model, and the Melson formula.

Understanding which model your state uses is essential for estimating what you might pay or receive. Use our Child Support Estimator to run the numbers for your specific situation.

The amount of child support ordered depends primarily on both parents' incomes, the number of children, and the custody arrangement. Additional factors include the cost of health insurance for the children, childcare expenses, and any special needs the children may have.

Most states review their guidelines every four years as required by federal law, so the specific tables and formulas change over time. Our calculator is updated to reflect the most current guidelines in each state.

Child support payments are not tax-deductible for the payer and are not taxable income for the recipient. This has been the rule for decades and was not changed by the 2017 Tax Cuts and Jobs Act (which did change the tax treatment of alimony).

This means that child support is transferred on an after-tax basis, which makes it more expensive per dollar than alimony was under the old tax rules. When negotiating your divorce settlement, understanding the after-tax cost of support is essential for realistic financial planning.

Child support enforcement is taken seriously at both the federal and state level. The federal Office of Child Support Enforcement (OCSE) coordinates interstate enforcement, and every state has a child support enforcement agency that can help custodial parents collect unpaid support through wage garnishment, tax reimbursement intercepts, license suspension, and other tools. Our guide on child support enforcement explains your options if your co-parent is not paying.

The Income Shares Model: Used by Most States

The income shares model is used by approximately 41 states and the District of Columbia, making it by far the most common approach. This model is based on the principle that children should receive the same proportion of parental income they would have received if the parents lived together.

The model calculates a combined parental income figure, looks up the total child support obligation on a state-specific schedule, and then divides that obligation between the parents based on their respective income shares. For a deeper comparison of the two main models, see our guide on income shares versus percentage of income.

For example, if Parent A earns $5,000 per month and Parent B earns $3,000 per month, their combined monthly income is $8,000. The state's child support schedule might indicate that the basic support obligation for one child at that income level is $1,200 per month.

Parent A earns 62.5% of the combined income, so Parent A's share would be $750 per month. Parent B's share would be $450, typically satisfied by direct spending on the child during their custodial time.

States using the income shares model include California, Florida, New York, Ohio, Pennsylvania, Virginia, and many others. Each state publishes its own income schedule, and the specific numbers can differ substantially.

California uses a complex algebraic formula under California Family Code §4055 that also heavily weights custodial timeshare. Use our California Child Support Estimator for state-specific calculations.

New York uses a hybrid approach under the Child Support Standards Act (New York Domestic Relations Law §240). The combined parental income up to $193,000 (periodically adjusted) 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 divided between the parents in proportion to their incomes. For income above the cap, the court has discretion to apply the formula or determine an amount based on the child's needs and the family's pre-separation standard of living. Try our New York Child Support Estimator for a calculation.

Florida's income shares model under Florida Statute §61.30 — the schedule tops at $10,000 of combined monthly net income; for incomes above $10K, courts add a statutory percentage (5% for one child, 7.5% for two, etc.) on the excess. The schedule accounts for the number of children and provides specific dollar amounts for the basic support obligation.

Florida also has one of the broadest parenting time credit systems, adjusting the support obligation when the noncustodial parent has the child for more than 20% of overnights. Use our Florida Child Support Estimator for state-specific results.

The Percentage of Income Model

A smaller number of states use the percentage of income model, which bases the child support obligation on the noncustodial parent's income alone, without considering the custodial parent's income. This model is simpler but arguably less equitable because it ignores one parent's earning capacity entirely.

Texas is the most prominent state using a flat percentage model. Under Texas Family Code §154.125, the noncustodial parent pays 20% of net resources for one child, 25% for two children, 30% for three, 35% for four, 40% for five, and not less than 40% for six or more children.

Net resources are capped, with the cap adjusted annually by the Office of the Attorney General. For 2026, the cap applies to the first $11,700 per month of net resources. Try our Texas Child Support Estimator for a quick calculation.

Wisconsin, Mississippi, and North Dakota also use variations of the percentage of income model, though some have modified their approaches to incorporate elements of the income shares model. The trend nationally is toward the income shares model, and several states that formerly used percentage of income have switched in recent years.

If your state recently changed models, older online calculators may give inaccurate results. Our Child Support Estimator is updated regularly to reflect current state guidelines.

The national trend is firmly away from the percentage model and toward income shares. Illinois switched from the percentage model to income shares in 2017.

Several other states have considered or are actively considering similar changes. If your state still uses the percentage model, be aware that a legislative change could affect future modifications of your support order. For a deeper comparison of the two models with numerical examples, see our article on income shares versus percentage of income.

The Melson Formula: Delaware, Hawaii, and Montana

The Melson formula, used by Delaware, Hawaii, and Montana, is a more sophisticated version of the income shares model. Developed by Judge Elwood F. Melson Jr. of Delaware Family Court, this formula adds a self-support reserve for each parent—ensuring that neither parent falls below a basic subsistence level—and includes a standard of living adjustment (SOLA) that gives children a share of any income above the parents' basic needs.

The Melson formula first deducts a self-support reserve (based on the federal poverty level) from each parent's net income. It then calculates the primary child support obligation based on the remaining income. If either parent's income after paying the primary obligation still exceeds the self-support reserve, a SOLA percentage is applied to the excess income and added to the child support amount.

While more complex, the Melson formula is considered by many family law scholars to be the most thoughtful approach because it balances the child's needs against each parent's ability to maintain a basic standard of living. In practice, the Melson formula often produces higher child support amounts for upper-income families and lower amounts for low-income families compared to the standard income shares model.

Factors That Increase or Decrease Child Support

Regardless of which model your state uses, several factors can adjust the basic child support calculation. The most significant factor in most states is the custodial timeshare—how much time the child spends with each parent.

In many income shares states, the child support obligation decreases as the noncustodial parent's custodial time increases, reflecting the direct expenses that parent incurs during their parenting time. See our article on how custody time affects child support for a detailed explanation.

Health insurance premiums for the children are typically added to the basic obligation and divided between the parents. Childcare costs necessary for a parent to work or attend school are handled similarly. Extraordinary medical expenses, special educational needs, and travel costs for long-distance visitation can also be added. Some states allow deductions for other children the paying parent supports, pre-existing support orders, and union dues or mandatory retirement contributions.

Income is broadly defined in most states and includes wages, salaries, commissions, bonuses, self-employment income, investment income, rental income, Social Security benefits, disability benefits, pensions, and more. If a parent is voluntarily unemployed or underemployed, courts in most states can impute income—attributing an earning capacity based on the parent's education, work history, and available job opportunities. This prevents a parent from reducing their support obligation by deliberately earning less.

Self-employment income presents unique challenges because business owners have more control over how they report income. Courts look beyond the tax return to examine the parent's actual cash flow, including personal expenses paid through the business, depreciation deductions that do not reflect actual cash expenditure, retained earnings, and non-cash benefits like company vehicles or meals. The IRS Publication 505 provides guidance on estimating income from self-employment, and courts often rely on forensic accountants to determine a self-employed parent's true income for support calculation purposes.

Military service members have specific child support rules. Under the Servicemembers Civil Relief Act (50 U.S.C. §§3901-4043), active-duty members may request stays of proceedings during deployment.

Military income for child support purposes includes base pay, housing allowance (BAH), subsistence allowance (BAS), and other special pays. The Defense Finance and Accounting Service (DFAS) can process income withholding orders for military members, making enforcement relatively straightforward compared to civilian cases.

High-Income and Low-Income Adjustments

Most state child support guidelines include income caps or supplemental provisions for high-income parents. When combined parental income exceeds the top of the guideline schedule—often $20,000 to $30,000 per month—courts have discretion to set support based on the child's reasonable needs, the family's pre-separation standard of living, and other equitable factors. In these cases, child support calculations become less formulaic and more dependent on the specific facts.

At the low end, most states include a self-support reserve or minimum order provision to prevent child support from pushing the paying parent below the poverty level. The federal Office of Child Support Enforcement (OCSE), part of the Administration for Children & Families, has issued guidance encouraging states to set orders that are realistic given the obligor's actual ability to pay. Orders that exceed a parent's ability to pay lead to arrearages, enforcement actions, and a cycle of debt that ultimately harms the child.

If you are concerned about your ability to pay—whether due to job loss, disability, or other changes in circumstances—you may be able to modify your child support order. Most states allow modification when there has been a substantial change in circumstances, such as a 15% to 20% change in income. Do not simply stop paying; unpaid child support accrues interest and can lead to serious enforcement consequences including wage garnishment, license suspension, and even jail.

How Parenting Time Affects the Calculation

In most income shares states, the amount of time each parent spends with the child directly affects the child support calculation. The logic is straightforward: the more time a child spends with a parent, the more that parent spends directly on the child's food, housing, clothing, and activities.

Many states use a parenting time credit or offset that reduces the noncustodial parent's obligation as their custodial time increases. Use our Custody Time Calculator to determine your custodial percentage based on your parenting schedule.

California's formula, for example, builds custodial time directly into the algebraic calculation under California Family Code §4055. A parent with 30% custodial time will pay more in support than a parent with 45% custodial time, all else being equal. Ohio applies a parenting time adjustment when the noncustodial parent has the child for more than 90 overnights per year, under Ohio Revised Code §3119.051.

The connection between custody and support creates important strategic considerations. Some parents seek more custodial time specifically to reduce their child support obligation—a practice that courts and custody evaluators scrutinize carefully. The court's primary concern is always the best interest of the child, and a request for additional parenting time that appears financially motivated may not be well received. Our guides on joint versus sole custody and creating a parenting plan explain how to approach custody decisions with the child's needs first.

The interplay between custody and support also affects relocation cases. If a custodial parent wants to relocate with the children and the move would reduce the noncustodial parent's time, the resulting change in custody percentage could increase the noncustodial parent's child support obligation.

Conversely, if the noncustodial parent gains more time as part of a compromise on relocation, their support obligation may decrease. These financial implications should be factored into relocation negotiations.

Child Support and College: An Emerging Issue

In most states, child support ends when the child turns 18 or graduates from high school, whichever is later. However, a growing number of states require or allow courts to order parents to contribute to college expenses.

States including New York, New Jersey, Connecticut, Massachusetts, Indiana, and others have statutes or case law authorizing college support orders. Our guide on child support and college expenses identifies which states require contributions and what factors courts consider.

Even in states where courts cannot order college support, parents can voluntarily agree to share college costs in their divorce settlement or parenting plan. These agreements are generally enforceable as contractual obligations, so it is important to draft them carefully with clear terms about which schools qualify, the maximum contribution amount, whether the child must maintain a minimum GPA, and how financial aid factors into the calculation.

Planning for college expenses early in the divorce process can prevent costly disputes later. If you and your co-parent can agree on a framework for sharing college costs, include it in your divorce decree. If you cannot agree, understand your state's law so you know whether the court has authority to order contributions and what standard it will apply.

The financial aid implications of divorce are also worth considering. The Free Application for Federal Student Aid (FAFSA) uses the custodial parent's income to determine financial aid eligibility.

If the custodial parent has a lower income, the child may qualify for more need-based financial aid than they would in an intact two-income household. However, some private colleges use a supplemental form (the CSS Profile) that considers both parents' finances regardless of custody.

Understanding how your custody arrangement affects college financial aid can save thousands of dollars in higher education costs. For more on this topic, see our detailed guide on child support and college expenses.

When and How to Modify Child Support

Child support orders are not permanent. Most states allow either parent to request a modification when there has been a substantial change in circumstances. Common grounds for modification include a significant increase or decrease in either parent's income, a change in the custody arrangement, a change in the child's needs (such as developing a disability or special educational requirement), or the emancipation of one child when there are multiple children on the order.

Many states define "substantial change" as a 10% to 20% change in the calculated support amount. Some states, including those following federal guidance under 45 CFR §303.8, require child support orders to be reviewed every three years upon request. Our guide on how to modify child support walks you through the process step by step.

Until a modification is granted by the court, you must continue paying the current order amount. Arrearages (unpaid past-due support) accrue from the date the modification petition is filed, not from the date circumstances changed. This means it is critical to file for modification as soon as possible after a qualifying change occurs. Most states charge a filing fee of $25 to $100 for modification petitions, and many allow self-represented filing with court-provided forms.

Getting an Accurate Estimate for Your Situation

The best way to understand what child support might look like in your case is to run the numbers through your state's official guidelines. Our Child Support Estimator covers all 50 states and applies each state's current formula, including adjustments for custodial timeshare, health insurance, and childcare costs. Select your state for a tailored calculation: California, Texas, Florida, New York, and all other states are available.

Keep in mind that online calculators provide estimates, not legal advice. The actual child support order in your case may differ based on factors that a calculator cannot capture—such as a child's extraordinary medical needs, a parent's disability, or income from complex sources like stock options or trust distributions. If your situation involves any of these complexities, consulting with a family law attorney is strongly recommended.

For families navigating both child support and custody decisions simultaneously, our Child Custody guide explains custody types, the factors courts consider, and how to build a parenting plan that works for your family. The support calculation and the custody arrangement are deeply interconnected, and understanding both will help you make better decisions throughout the divorce process.