Updated: 2026-06-11
Quick answer: Child support is set at the state level, and almost every state uses one of three formulas. The income-shares model (about 41 states) combines both parents’ incomes and splits the obligation by share. The percentage-of-income model (about 7 states, including Texas) bases support on a share of the paying parent’s income. The Melson formula (Delaware, Hawaii, and Montana) protects each parent’s basic needs first. A federal framework under Title IV-D ties them together — every state runs a child support agency and a State Disbursement Unit, and federal tools like tax-refund intercepts and passport denial at $2,500 in arrears apply nationwide. To estimate your amount, use your own state’s official calculator or guidelines.
Legal disclaimer: This article is general information, not legal advice. Child support rules and amounts vary by state and change over time. For your specific situation, consult a family-law attorney licensed in your state.
Child support is one of the few family-law topics decided almost entirely at the state level, so the rules that apply to you depend on where your case is heard. Two parents with identical incomes can owe very different amounts in different states. This guide explains the three formulas states use, compares the states we cover in depth, and shows how to find the official calculator and agency for any state.
Table of Contents
- How is child support calculated by state?
- Which states use the income-shares model?
- Which states use the percentage-of-income model?
- Which states use the Melson formula?
- State-by-state child support guides
- How do you find your state’s child support agency and calculator?
- What is the same in every state?
- How is child support enforced across state lines?
- When does child support end?
- Frequently Asked Questions
How is child support calculated by state?
Every state has its own written child support guidelines, but they fall into just three families. The National Conference of State Legislatures groups them as the income-shares model, the percentage-of-income model, and the Melson formula. Knowing which one your state uses tells you what actually drives the number.
| Model | How it works | Roughly how many states | Examples |
|---|---|---|---|
| Income shares | Combine both parents’ incomes, find the obligation on a schedule, split it by each parent’s share | ~41 states | Colorado, Indiana, Florida, Ohio, California |
| Percentage of income | Apply a percentage to the paying parent’s income; the other parent’s income isn’t the focus | ~7 states | Texas |
| Melson formula | Like income shares, but protects each parent’s basic needs first, then shares extra income with the child | 3 states | Delaware, Hawaii, Montana |
The model matters most when parents earn very different amounts. Income-shares and Melson states look at both incomes, so a high-earning custodial parent can lower what the other owes; a flat percentage-of-income state mostly looks at the payer.
Which states use the income-shares model?
The income-shares model is by far the most common — about 41 states and two territories. It rests on a simple principle: a child should get the same share of the parents’ combined income they would have received if the household stayed intact. The state combines both parents’ incomes, matches them to a support schedule to find a basic obligation, and divides that obligation in proportion to what each parent earns. Parenting time, childcare, and health costs then adjust the result.
States we cover in depth that use this model include Colorado, Indiana, Florida, and Ohio. California uses a related approach — a statewide algebraic formula built on both parents’ net incomes and parenting time.
Which states use the percentage-of-income model?
About seven states use the percentage-of-income model, which looks primarily at the paying parent’s income and applies a percentage based on the number of children. Four of those states use a flat percentage that doesn’t change with income level. Texas is the best-known example: it sets support as a percentage of the paying parent’s net resources — 20% for one child, 25% for two, and so on — up to a cap.
The trade-off is simplicity versus precision. A percentage-of-income order is easy to predict, but it doesn’t directly account for the receiving parent’s income the way an income-shares order does.
Which states use the Melson formula?
Only three states — Delaware, Hawaii, and Montana — use the Melson formula, the most complex of the three. Named for Delaware Family Court Judge Elwood Melson, it works like income shares but adds a step: it first sets aside enough income for each parent’s basic self-support needs, then calculates child support, and finally allows the child to share in any income left over above those needs. The result is a formula designed to keep low-income parents solvent while still letting children benefit when a parent earns more.
State-by-state child support guides
Below are the states we cover with a full guide — how the formula works, the official calculator or worksheet, how to apply and pay, how to modify, and when support ends. The model, administering agency, and ending age vary, so the right starting point is your own state.
| State | Model | Who runs it | Support generally ends | Full guide |
|---|---|---|---|---|
| Texas | Percentage of obligor’s net resources | Office of the Attorney General | 18 or high school graduation | Texas guide |
| California | Statewide guideline formula (income-based) | Dept. of Child Support Services | 18, or 19 if in high school | California guide |
| Colorado | Income shares | Division of Child Support Services | 19 | Colorado guide |
| Indiana | Income shares | Child Support Bureau (DCS) | 19, plus possible college support | Indiana guide |
| Florida | Income shares | Department of Revenue | 18, or 19 if in high school | Florida guide |
| Ohio | Income shares | County CSEAs (ODJFS) | 18, or 19 if in high school | Ohio guide |
If your state isn’t listed yet, the next section shows how to find its official program and calculator.
How do you find your state’s child support agency and calculator?
Every state runs a child support program under the federal Title IV-D framework, so there is always an official agency and, in most states, an official way to estimate support. The fastest path:
- Start with the federal directory. The federal Office of Child Support Services publishes a state and tribal child support agency directory that links to every state’s program — the single most reliable place to find your state’s official site.
- Look for the official calculator. Some states (California, Indiana, Texas) offer a free public calculator; others (Florida, Ohio) provide an official worksheet that your local agency or attorney completes. Use the state’s own tool, not a generic estimator, because the schedule and adjustments differ.
- Find your local office. Most states deliver services through county or regional offices. Your state agency site links to the office that handles your case.
Be cautious with third-party “child support calculators.” They can be a useful rough guide, but only the state’s official tool reflects the current schedule, the parenting-time rules, and recent changes.
What is the same in every state?
State formulas differ, but federal law under Title IV-D of the Social Security Act (see 42 U.S.C. § 651) creates a common backbone. No matter where you live, these hold true:
- A State Disbursement Unit (SDU) processes payments. You pay the SDU, not the other parent directly, which creates the official record.
- Income withholding is the default. Most orders are paid through automatic wage withholding.
- Federal enforcement tools apply. Unpaid support can trigger federal tax-refund intercepts and passport denial once arrears reach $2,500.
- States can suspend licenses and report debt. Driver’s, professional, and recreational license suspension, liens, and credit-bureau reporting are standard tools.
- Both parents’ income is documented. Even percentage-of-income states require financial disclosure.
This federal layer is why a parent who moves across the country still can’t simply walk away from an order.
How is child support enforced across state lines?
When parents live in different states, the Uniform Interstate Family Support Act (UIFSA) governs which state controls the order and how it’s enforced. Adopted by every state, UIFSA ensures that only one valid support order exists at a time — the “controlling order” — and lets one state enforce an order issued by another.
In practice, your local child support agency can work with another state’s agency to collect, and federal tools like tax intercepts and passport denial follow the parent regardless of where they move. If you relocate, tell your child support agency promptly; moving does not change the order on its own, and arrears keep accruing under the controlling order. Our guide to how the custody court process works explains how jurisdiction is established in the first place.
When does child support end?
The ending age varies by state, but most cluster around 18 or 19. Common rules:
- Age 18 with a high-school extension — many states (Texas, Florida, Ohio, California) end support at 18 but continue it until high school graduation, capped around 19.
- Age 19 outright — a few states (Colorado, Indiana) use 19 as the standard age of emancipation.
- College support — most states do not require it, but a handful (including Indiana) let a court order parents to contribute to post-secondary education.
- Early end — marriage, military enlistment, or becoming self-supporting can end support sooner.
- Disability — support can continue indefinitely for a child who can’t support themselves because of a disability that began before adulthood.
Because the specifics differ, check your state’s guide before assuming support stops on a particular birthday. If you and the other parent can agree on terms, our guide to reaching a custody agreement without a court fight is a good starting point.
Frequently Asked Questions
How is child support calculated by state?
Almost every state uses one of three formulas. The income-shares model (about 41 states) combines both parents’ incomes and splits the obligation by share. The percentage-of-income model (about 7 states, including Texas) applies a percentage to the paying parent’s income. The Melson formula (Delaware, Hawaii, and Montana) protects each parent’s basic needs before calculating support. To get an accurate figure, use your own state’s official calculator or guidelines worksheet.
Which child support model is most common?
The income-shares model is by far the most common, used by about 41 states and two territories. It combines both parents’ incomes, finds a basic obligation on a state schedule, and divides it in proportion to each parent’s income, then adjusts for parenting time, childcare, and health costs. Colorado, Indiana, Florida, and Ohio all use it, and California uses a related income-based formula.
Does child support vary a lot from state to state?
Yes. Because each state writes its own guidelines and chooses its own model, two parents with identical incomes can owe very different amounts depending on where the case is heard. Income-shares and Melson states weigh both parents’ incomes; percentage-of-income states focus on the payer. Caps, minimums, parenting-time adjustments, and ending ages also differ, which is why the state-specific guide matters.
How do I find my state’s child support calculator?
Start with the federal Office of Child Support Services directory of state and tribal agencies, which links to every state’s official program. From there, look for the state’s own calculator or guidelines worksheet — some states offer a free public calculator, while others provide a worksheet completed by the agency or an attorney. Avoid relying on generic third-party calculators, since only the official tool reflects the current schedule and rules.
What happens to child support if a parent moves to another state?
The Uniform Interstate Family Support Act (UIFSA) keeps one controlling order in place and lets states enforce each other’s orders. Moving does not cancel or change support on its own; the order keeps running, and federal tools like tax-refund intercepts and passport denial follow the parent. Notify your child support agency when you move so the case can be transferred or coordinated correctly.
At what age does child support end?
It depends on the state. Many states end support at 18 but extend it until high school graduation, usually capped at 19. A few states use 19 as the standard age. Most states don’t require college support, though some let a court order it. Support can end earlier if the child marries, joins the military, or becomes self-supporting, and it can continue for a child with a qualifying disability.
Note: This article is general information, not legal advice. Child support laws and amounts vary by state and change over time. For decisions about your specific situation, consult a family-law attorney licensed in your state.
