What is the child support formula used in each state?

Last updated 2026-07-10

Why does child support have a formula at all?

Congress passed the Child Support Enforcement Amendments of 1984 and then the Family Support Act of 1988. Both required every state to adopt numeric child support guidelines and make those guidelines the legal presumption in any court order ^[1]. Before that, awards were wildly inconsistent, often arbitrary, and almost always too low.

The federal requirement is blunt. States must review their guidelines at least every four years, and any deviation from the guideline amount requires a written finding explaining why the guideline result would be "unjust or inappropriate" ^[1]. That phrase comes straight out of 45 CFR § 302.56, the federal regulation.

So the formula isn't optional. A judge who ignores the guideline number without explanation is reversible on appeal. That gives the number real weight, even in cases where both parents would rather use a different one.

What states control is which formula to use. The federal government sets the floor (you must have guidelines), not the ceiling (you can design them however you want, within reason). That's why the math looks so different depending on where you live.

What are the three child support models states use?

There are three models in use across the country. The map has shifted over time, but recent state policy surveys put the breakdown like this ^[2]:

Model	States Using It (approx.)	Core Mechanic
Income Shares	~40 states	Both parents' incomes combined; obligation split by share
Percentage of Income	~9 states	Only the paying parent's income counts
Melson Formula	3 states (DE, HI, MT)	Income Shares with a self-support reserve layer

Income Shares is the dominant model. The idea is that a child should get the same proportion of parental income the child would have gotten if the family stayed together. You add both parents' gross incomes, look up the total obligation on a schedule, and each parent pays their proportional share. The noncustodial parent pays their share to the custodial parent. The custodial parent's share is presumed spent directly on the child.

Percentage of Income looks only at the paying parent. Some versions are "flat" (the same percentage at every income level) and some are "varying" (the percentage changes at different income bands). Wisconsin is the classic flat-rate state: 17% of gross income for one child, 25% for two, 29% for three, 31% for four, 34% for five or more ^[3].

Melson Formula is Income Shares with an extra step. Before the child's share gets calculated, each parent keeps a "self-support reserve," a minimum amount of income for their own basic needs. Delaware built this model in the 1970s. It's the most protective of a parent's own survival, and also the most complex to run.

Knowing which bucket your state falls into tells you which inputs matter. In an Income Shares state, both incomes carry roughly equal weight. In a Percentage of Income state, one income (yours or your co-parent's) is the whole ballgame.

Which model does each state use?

The National Conference of State Legislatures and the Office of Child Support Services both keep state-by-state breakdowns ^[2][4]. Here's the full picture as of the most recent federal review cycle:

Income Shares states (approximately 40): Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wyoming

Percentage of Income states (approximately 9): Mississippi, Nevada (varying), North Dakota, Texas, and Wisconsin use percentage-of-income models, plus a handful of others depending on how you classify hybrid rules. Texas uses a flat percentage applied to net resources: 20% for one child, 25% for two, 30% for three, 35% for four, 40% for five, and not less than 40% for six or more ^[5].

Melson Formula states: Delaware, Hawaii, and Montana.

A few states run hybrid rules or have updated their models recently, so check your state court's self-help center for the current schedule. Guidelines change. A table written in 2021 may not match a 2024 revision.

If you're in the middle of an uncontested divorce and trying to land on a child support figure you and your co-parent can both live with, run the actual state calculator first. Most state child support agencies publish one free online, and it gives you a defensible starting number. A judge is very unlikely to approve a settlement that departs from the guideline without a written explanation.

How does the Income Shares calculation actually work?

Take a real example. Two parents in Ohio (an Income Shares state) have one child. Parent A earns $5,000 per month gross. Parent B earns $3,000 per month gross. Combined income is $8,000.

Ohio's schedule puts the basic child support obligation for one child at $8,000 combined monthly income at roughly $1,321 ^[6]. Parent A's share of combined income is 62.5% ($5,000 / $8,000), so Parent A's obligation is about $826. Parent B's share is 37.5%, or about $495.

If Parent B is the residential parent (the child lives with Parent B), Parent A pays $826 per month. Parent B is presumed to spend their $495 directly.

That's the basic math. Then you layer on adjustments:

• Work-related childcare costs. These get added to the basic obligation and split proportionally.
• Health insurance premiums. The cost of the child's portion of a parent's employer plan gets added to the pot and split.
• Parenting time adjustments. Most Income Shares states cut the paying parent's obligation once they cross a threshold number of overnights per year, because they're spending money directly during that time.

The Ohio Supreme Court publishes a child support worksheet that walks through all of these adjustments step by step ^[6]. Most Income Shares states use a nearly identical worksheet, just with different dollar amounts on the schedule.

How does the Percentage of Income calculation work?

In Texas, which uses a percentage of net resources, the math starts differently. First you calculate the paying parent's "net resources," which is not the same as take-home pay. Texas Family Code § 154.062 defines net resources as gross income minus federal income tax (based on the tax rate for a single person claiming one exemption), Social Security taxes, Medicare taxes, union dues, and health insurance premiums for the children ^[5].

Once you have net resources, you apply the percentage. One child = 20%. The maximum net resources subject to the percentage cap is $9,200 per month as of the 2023 guidelines update ^[5]. Above that cap, more support requires a separate finding of the child's actual needs.

So a Texas parent with net resources of $4,000 per month pays $800 for one child. Simple. The custodial parent's income never enters the formula in a flat percentage state.

Wisconsin's percentage applies to gross income, not net. That's a big difference. Read your state's statute carefully on this point, because "income" is defined differently almost everywhere.

Mississippi uses a percentage-of-adjusted-gross-income table with rates that vary by the number of children, from 14% for one child to 22% for five or more ^[7]. Mississippi doesn't count the custodial parent's income in the base calculation, though it can surface in a deviation argument.

What counts as income for child support purposes?

This is where people get surprised. Income for child support is broader than what shows up on a W-2.

Most states include: wages and salary, self-employment income (gross receipts minus ordinary and necessary business expenses), overtime (courts differ on whether voluntary overtime must be counted), bonuses, commissions, dividends and interest, rental income, pension and retirement benefits, Social Security disability and retirement benefits, veterans' benefits, workers' compensation, and unemployment.

Federal law, specifically 42 U.S.C. § 666, requires states to have procedures to impute income when a parent is voluntarily unemployed or underemployed ^[8]. A parent who quits a $90,000 job to earn $12,000 doing something else doesn't automatically get a much lower order. The court can attribute income at the higher level if it finds the reduction was voluntary and not in good faith.

What's generally excluded: public assistance (TANF, SSI in most states), child support received for other children, and in some states, housing allowances for military members (this varies).

Self-employed parents are the hardest cases. Business expenses that legitimately reduce net profit for tax purposes may or may not reduce income for child support, depending on whether they're truly necessary or effectively personal expenses run through the business. Courts look hard at this.

What can a court adjust the formula result up or down for?

The guideline number is the presumptive amount, not the final word. Every state has a list of factors a court can use to deviate from the formula result, but a judge has to explain any deviation in writing.

Common deviation factors across state guidelines:

• Extraordinary medical expenses for the child that the worksheet doesn't already capture
• Educational costs, including private school tuition if the child was enrolled before the divorce
• A parent's other child support obligations for children from other relationships
• The child's standard of living before the divorce, in high-income cases
• A parent's significant debt taken on for the family's benefit
• Shared physical custody arrangements that don't fit neatly into the parenting-time adjustment formula
• Travel costs for long-distance parenting

In very high-income cases, the guideline result can look huge next to what the child actually needs. Many states cap the formula at a combined income level (Texas caps at $9,200 net resources per month; California has its own high-income rules) and then require a separate needs-based analysis above that cap.

Deviations aren't rare, but they aren't automatic either. If you and your co-parent settle on a number that differs from the guideline, your settlement agreement or parenting plan needs a specific written reason. Most state family law forms have a spot for it. Without it, the judge will likely send the paperwork back.

Does child support change if parenting time changes?

Yes. In most Income Shares states, more parenting time for the paying parent means a lower child support obligation. The logic is that the paying parent covers direct costs (food, housing, activities) during their time, so making them also pay the full formula amount double-counts.

The threshold and adjustment mechanism vary by state. In Virginia, a "shared custody" adjustment kicks in when either parent has the child more than 90 days per year ^[9]. California's DissoMaster formula (used by courts to run support) automatically reduces the noncustodial parent's obligation as their share of parenting time goes up ^[10].

In a true 50/50 arrangement, the formula result can drop hard, sometimes to zero if the parents' incomes are close. But if one parent earns a lot more, even equal parenting time produces a support obligation running from the higher earner to the lower earner, because the goal is equalizing the child's living standard across two households.

Parenting-time adjustments are one of the most litigated areas in child support modification. If you're negotiating a parenting plan in an uncontested divorce, the number of overnights matters financially, more than emotionally. Run the numbers under a few different scenarios before you lock the schedule.

To see how your parenting plan moves the number, a free child support calculator built for your state is the fastest starting point.

How often can child support be modified, and what triggers a review?

Federal regulations require states to review child support orders at either parent's request at least once every three years when the family gets Medicaid or Title IV-D child support services ^[1]. Outside those cases, modification rules vary.

Most states allow modification after a "substantial change in circumstances" since the last order. What qualifies:

• A significant income change for either parent (many states define "significant" as 15% to 20% or more)
• A change in the child's needs (new medical diagnosis, change in healthcare costs)
• A change in the parenting schedule
• One of several children reaching the age of majority

Some states use a shortcut: if running the current formula on today's numbers produces a result that differs from the existing order by at least a set percentage, that gap alone is enough grounds to modify, no other change required. Oregon uses a 15% threshold ^[11].

You can't modify child support by private agreement alone. Even if both parents agree to change the amount, a court has to approve the change and enter it as a new order. An informal handshake to pay less is legally unenforceable and leaves the paying parent liable for arrears on the original order.

This is one of the spots where careful paperwork pays off. A properly filed stipulation to modify child support, signed by both parents and entered by the court, protects both of you.

What's different about child support in an uncontested divorce?

In a contested divorce, a judge sets child support after reviewing financial evidence. In an uncontested divorce, you and your co-parent work out the number yourselves and ask the court to approve it.

The approval isn't a rubber stamp. Courts take child support seriously because it protects the child, more than the parents. Most family court judges check whether the agreed amount matches the state guideline. If it doesn't, they want a written explanation.

The practical move: before you finalize your settlement agreement, run the state formula with both parents' actual incomes. Write that calculation down. If you're agreeing to a different amount, document why. Some states have a specific form for child support worksheets that has to be filed with your divorce paperwork.

For an uncontested divorce with children, your divorce papers packet needs more than the petition and settlement agreement. It also needs a parenting plan and a child support worksheet or order. Miss any of these and your case stalls.

DivorceClear's $149 document packet includes state-specific child support worksheets along with the rest of your uncontested divorce paperwork, so you're not hunting through court websites trying to figure out which forms your county actually wants.

If you have specific legal questions about your situation, talk to a divorce attorney. What's here is general information, not legal advice for your case.

Where can you find your state's official child support calculator?

Every state has a child support enforcement agency, and most publish a free calculator online. These are the most reliable tools because they get updated when the guidelines change.

The federal Office of Child Support Services keeps a directory of state child support agencies at its website ^[4]. From there, look for a link to the state's child support guidelines, worksheet, or calculator. Some states (Ohio, Virginia, California) have particularly good online calculators. Others make you download a spreadsheet.

A few trusted starting points:

• Federal OCSS state resource directory: acf.hhs.gov (search "state child support agencies")
• Your state court's self-help center: search "[state name] family court self-help center"
• Your state's child support enforcement agency: usually a division of the state Department of Health and Human Services or its equivalent

Skip third-party calculators that don't cite the specific guideline schedule they're using. The numbers change when states revise their guidelines, and a stale calculator gives you a stale number. When both parents are going to agree to an amount in an uncontested divorce, you want the number that matches what the court expects to see.

The National Conference of State Legislatures also publishes periodic summaries of state child support guideline structures ^[2]. It's a solid high-level reference, though it doesn't replace the actual state worksheet.

Some states post PDF copies of their guideline tables in their court rules or administrative code. In California, for example, Family Code § 4055 holds the actual formula ^[10]. Reading the statute directly is dense, but it's the most authoritative source you can cite.

Frequently asked questions

Does the higher-earning parent always pay child support?

Usually, but not always. In Income Shares states, both parents have an obligation proportional to their income. If the higher earner is also the primary residential parent, the lower-earning parent may pay support to them. The formula focuses on the child's total needs and each parent's proportional ability to contribute, not simply on who earns more. Parenting time also factors in and can shift the direction or amount.

Can parents agree to waive child support entirely?

Courts almost never approve a zero child support order unless the paying parent has zero income and no income-earning capacity. Child support belongs to the child, not to the parents, so parents can't waive it on the child's behalf. A judge reviewing an uncontested divorce will look closely at any agreed amount well below the guideline and can reject the settlement if it doesn't adequately protect the child.

Is child support based on gross income or net income?

It depends on the state. Federal law doesn't specify. Most Income Shares states use gross income before taxes. Texas uses net resources after defined deductions. Wisconsin uses gross income. Massachusetts uses gross income but then applies specific deductions. Always check your state's guideline statute or worksheet, because "income" is defined precisely in each state's rules, and using the wrong base produces the wrong number.

What happens if a parent refuses to disclose their income?

Courts can impute income based on earning capacity, work history, education, and local job market data when a parent won't provide financial documentation. In contested cases, a court can hold a parent in contempt for refusing to comply with financial disclosure orders. In an uncontested divorce, both parents usually provide income documentation voluntarily, but if one refuses, the case likely becomes contested.

Does child support cover college expenses?

Not automatically. Basic child support typically ends when the child reaches the age of majority, 18 in most states or 19 in a few. Some states (Indiana, for example) let courts order post-secondary educational support beyond age 18 under specific circumstances. Others don't permit it at all. Parents can agree to cover college costs in their settlement agreement even where the statute doesn't require it, but courts vary on whether they'll enforce such agreements.

How does remarriage affect child support?

A parent's remarriage generally doesn't by itself change their child support obligation. A new spouse's income isn't counted as the parent's income in most states. But if remarriage substantially changes a parent's household expenses (a spouse now covers the mortgage, say), it could be one factor in a modification analysis. The focus stays on the biological or adoptive parents' own incomes and the child's needs.

What is the Melson Formula and which states use it?

The Melson Formula is a variation of Income Shares developed in Delaware in the 1970s. It adds a self-support reserve: each parent keeps enough income to cover their own basic subsistence before any child support gets calculated. Delaware, Hawaii, and Montana use it. It's the most protective of low-income parents and the most complex to run. The result is usually close to what a standard Income Shares formula produces for middle-income parents.

Does child support automatically end when the child turns 18?

In most states, yes. Some states extend it to 19 if the child is still in high school. New York continues support to age 21. A few states allow extension for disabled adult children. The order doesn't end automatically in every jurisdiction; some require a formal filing. Check your state's statute and your specific order language. Paying past the end date doesn't get you a refund, but failing to pay before it ends creates arrears.

Can child support be included in an uncontested divorce if both parents agree on the amount?

Yes, and this is the normal path in an uncontested divorce. You include the agreed amount in your marital settlement agreement or a separate child support order, attach the required state worksheet showing the guideline calculation, and note in writing if your agreed amount differs from the guideline and why. The court reviews and approves it. Missing the worksheet is a common reason courts return uncontested divorce paperwork for correction.

What's the difference between a child support order and a child support agreement?

A child support order is a court-entered document with legal enforcement power. Child support can be collected through wage garnishment, tax refund interception, and license suspension only when there's a court order. A private agreement between parents, even in writing, isn't enforceable through those mechanisms. Any agreed amount has to be submitted to the court and entered as an order to carry full legal force.

How do I find my state's child support guideline worksheet?

Start at your state child support enforcement agency's website or your state court's self-help center. The federal Office of Child Support Services at acf.hhs.gov keeps a directory of state agencies. Many states post the PDF worksheet directly on their court websites. Search your state name plus 'child support worksheet' or 'child support guidelines schedule.' Use only official .gov sources so you know you have the current version.

Does the child support formula account for health insurance costs?

Yes. Most Income Shares states add the cost of the child's health insurance premium (the portion attributable to the child in a family plan) to the basic obligation and split it proportionally between parents. Unreimbursed medical expenses are often split separately, either proportionally or 50/50 depending on the state's rules. In a Percentage of Income state like Texas, health insurance premiums for the children reduce the paying parent's net resources before the percentage is applied.

Sources

1. U.S. Code of Federal Regulations, 45 CFR § 302.56 (child support guidelines requirements): Federal law requires states to have numeric child support guidelines as the legal presumption in all orders, reviewed at least every four years, with written findings required for any deviation.
2. National Conference of State Legislatures, Child Support Guideline Models by State: Approximately 40 states use the Income Shares model, about 9 use a Percentage of Income model, and 3 states (Delaware, Hawaii, Montana) use the Melson Formula.
3. Wisconsin Department of Children and Families, Child Support Percentage Standards: Wisconsin's flat percentage standard is 17% of gross income for one child, 25% for two, 29% for three, 31% for four, and 34% for five or more children.
4. U.S. Department of Health and Human Services, Office of Child Support Services, State Resources: The federal OCSS maintains a directory of state child support agencies and requires states to review orders every three years for families receiving Medicaid or Title IV-D services.
5. Texas Family Code § 154.062 and § 154.125, Child Support Net Resources and Percentages: Texas applies child support percentages to net resources after defined deductions; rates are 20% for one child up to 40% for five or more, with a $9,200 per month net resources cap as of 2023 guidelines.
6. Ohio Supreme Court, Child Support Guideline Worksheet and Schedule: Ohio's Income Shares schedule sets the basic child support obligation for one child at a combined monthly gross income of $8,000 at approximately $1,321.
7. Mississippi Department of Human Services, Child Support Guidelines: Mississippi's percentage-of-adjusted-gross-income model ranges from 14% for one child to 22% for five or more children, applied only to the paying parent's income.
8. 42 U.S.C. § 666, Federal Requirements for Child Support Enforcement: Federal law requires states to have procedures to impute income to parents who are voluntarily unemployed or underemployed when calculating child support obligations.
9. Virginia Code § 20-108.2, Child Support Guidelines and Shared Custody Adjustment: Virginia's shared custody adjustment applies when either parent has the child more than 90 days per year, reducing the noncustodial parent's base support obligation.
10. California Family Code § 4055, Statewide Uniform Child Support Guideline Formula: California's guideline formula is contained in Family Code § 4055 and incorporates both parents' net disposable incomes and each parent's approximate time with the child.
11. Oregon Department of Justice, Child Support Guidelines and 15% Modification Threshold: Oregon allows child support modification when applying current guidelines produces a result that differs from the existing order by 15% or more.