Child support is a court-ordered payment from one parent to another for the financial care of their children after separation or divorce. Unlike alimony (spousal support), which judges may adjust with broad discretion, child support in nearly every U.S. state begins with a published formula or guideline worksheet—not an open-ended guess. Legislatures and state courts adopt these guidelines so parents, attorneys, and judges start from the same baseline before applying adjustments for health insurance, child care, parenting time, and other statutory factors. There is no single federal child support formula for routine domestic cases, though federal policy requires each state to maintain guidelines and review them periodically. All 50 states and the District of Columbia have their own statutes, administrative rules, and worksheets. The two dominant approaches nationwide are the income shares model (used in 38 states, including California, Colorado, Florida, Illinois, New York, Ohio, and Pennsylvania) and the percentage of income model (used in 12 states, including Texas, Mississippi, and Wisconsin). A few jurisdictions, notably California, apply hybrid formulas that combine income-shares logic with parenting-time and high-income adjustments under state family code.
Income Shares Model (38 States)
Under the income shares model, both parents are treated as financially responsible for the child in proportion to their earnings. Courts (or administrative agencies) first combine the parents' gross monthly incomes, then look up a basic support obligation from the state's guideline table for the number of children. Each parent pays a share of that obligation equal to their percentage of combined income, before credits for parenting time, health insurance, and other add-ons.
This model is used in 38 states, including California, Colorado, Florida, Illinois, Indiana, Massachusetts, Michigan, Minnesota, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Virginia, and Washington, among others. The statutory base is typically both parents' gross monthly income, though some states allow deductions for taxes, mandatory retirement, and other items defined by rule.
Example (illustrative): Parent A earns $6,500 per month; Parent B earns $4,200 per month. Combined income is $10,700. For two children, assume the state guideline table assigns a basic obligation of $1,800 per month. Parent A's share of combined income is 60.75% ($6,500 ÷ $10,700). Parent A's presumptive share before adjustments is approximately $1,093 per month (60.75% × $1,800). Parent B would owe the remainder unless parenting-time or other credits apply. Actual worksheet lines vary by state; always use your state's official form or calculator.
Percentage of Income Model (12 States)
In the percentage of income model, only the non-custodial parent's income is multiplied by a fixed percentage that rises with the number of children. The custodial parent's income is not part of the base calculation, though some states modify the result for shared parenting or low-income obligors.
Twelve states use this approach, including Minnesota (for higher-income cases under state rules), Mississippi, Missouri, Nevada, North Dakota, South Dakota, Texas, and Wisconsin, among others. Texas is the most commonly cited example because its percentages are set by statute.
Texas example: Under Tex. Fam. Code § 154.125, guideline percentages apply to the obligor's net monthly resources: 20% for one child, 25% for two, 30% for three, 35% for four, and 40% for five or more children (slightly different caps may apply when the obligor has children in multiple households). If net monthly resources are $5,000 and the obligor has two children in the case, the guideline amount is $5,000 × 25% = $1,250 per month before medical support, dental insurance, or other court-ordered additions. Texas courts apply the guidelines unless a party rebuts the presumption with evidence that the guideline amount is unjust or inappropriate.
California: Hybrid Formula
California does not use a simple flat percentage. Courts apply a hybrid formula under Cal. Fam. Code § 4055: CS = K × (HN − (H%)(TN)), where K is a factor based on the high earner's proportion of parenting time, HN is the high earner's net monthly disposable income, H% is the high earner's percentage of parenting time, and TN is total net monthly disposable income of both parents. California uses net (not gross) income after allowable deductions defined by statute and rule.
This structure means that as the higher-earning parent spends more overnights with the child, the formula can reduce or shift the payment direction. Health insurance, mandatory union dues, and other adjustments are applied on the state worksheet after the base computation.
Factors That Increase or Reduce Support
Every state guideline starts with income and number of children, then applies common adjustments:
- Parenting time / overnights: More time with the obligor often reduces cash support under income shares and some percentage states, because the parent is already paying day-to-day costs during their custody periods. - Health insurance and uninsured medical costs: Premiums and extraordinary medical expenses are frequently split by income share or ordered in addition to base support. - Child care: Work-related day care and mandatory school-age care costs are often added to the obligation and allocated between parents. - Other dependents: A parent's legal duty to support other children (in or outside the home) may reduce available income on the worksheet. - Deviation from the guideline: Courts may depart from the presumptive amount for documented hardship, special needs, very high income, or other factors listed in state statute—but the moving party usually must justify the deviation with evidence.
These adjustments are why two families with similar incomes can receive different orders after a judge signs the final worksheet.
How to Use the Child Support Calculator
TheLegalCalc's free Child Support Calculator applies your state's guideline framework using inputs you provide: each parent's income, number of children, approximate parenting-time share, and optional costs for health care and child care. Select your state to align the estimate with the income shares, percentage of income, or hybrid rules that apply where your case is filed.
The tool is designed for planning and education—it shows how the arithmetic changes when income or overnights shift. It does not replace a court order, a state judicial council worksheet, or advice from a licensed family law attorney. For a formal filing, use the official forms published by your state court or child support agency, then compare with our calculator to sanity-check the numbers before mediation or a hearing.
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Open Child Support CalculatorFrequently asked questions
There is no single national formula. Each state publishes child support guidelines under its family code or administrative rules. Most states (38) use the income shares model: combine both parents' incomes, look up a basic obligation for the number of children, and split that amount in proportion to each parent's share of earnings. Twelve states, including Texas, use a percentage of income model that applies a statutory percentage to the non-custodial parent's income (Texas sets rates in Tex. Fam. Code § 154.125). California uses a hybrid formula under Cal. Fam. Code § 4055 based on net income and parenting time. After the base amount, courts add or credit health insurance, child care, and parenting-time adjustments. Federal law requires states to maintain guidelines but does not replace state worksheets for routine cases.
Yes. Guidelines produce a presumptive amount, but courts may deviate when a party shows that applying the guideline would be unjust or inappropriate under state law. Common reasons include extraordinary medical needs, very high or very low income, shared parenting that does not fit the worksheet defaults, or financial hardship. In Texas, Tex. Fam. Code § 154.125 creates a rebuttable presumption in favor of the guideline; the party seeking a different amount must present evidence. In income shares states, judges typically complete the full worksheet first, then enter findings explaining any departure. Agreed settlements still require court approval in most jurisdictions and must generally explain how the agreed amount serves the child's best interest.
Usually yes. Guideline tables and percentage schedules increase with the number of children covered by the order. If you have additional children in another relationship, many states allow a credit or deduction for existing legal support obligations or dependents living in your home, which can lower the income available for a new calculation—but the rules differ widely. In Texas, the percentage applied under § 154.125 depends on how many children are before the court, with separate provisions when the obligor supports children in multiple households. A new child does not automatically reduce an existing order; you typically must file a modification motion and show a material change in circumstances under state law.
Parenting time matters most in income shares and hybrid states. The more overnights the obligor has, the more they are presumed to spend directly on the child, which can reduce cash transfer to the other parent. California's § 4055 formula explicitly incorporates the high earner's time share (H%). In pure percentage states such as Texas, parenting time may not change the base percentage unless the parents qualify for shared custody adjustments or a court-ordered deviation. Even when time share lowers base support, add-ons for health insurance and child care may still apply. Always use the parenting-time definition in your state's worksheet—some states count overnights, others use a different threshold for a "shared" arrangement.
Child support is a court order. Unpaid amounts accrue as arrears, which generally cannot be discharged in bankruptcy. States enforce orders through wage garnishment, tax refund intercepts, license suspension (driver's, professional, or recreational), liens, and contempt proceedings that may include fines or jail for willful nonpayment. Federal law also allows interstate enforcement through the Uniform Interstate Family Support Act (UIFSA). If your income drops, you must petition the court for a modification; simply paying less without a new order leaves arrears growing. Enforcement agencies and private attorneys can pursue collection, but the remedy is separate from the guideline calculation itself—obligation amounts are set by formula and order, while enforcement is handled under state and federal collection statutes.
This guide provides general information only and does not constitute legal advice. Child support amounts are determined by courts based on your specific circumstances. Consult a licensed family law attorney in your state.