How child support is calculated in the United States.
Every state publishes a child-support guideline, and every guideline answers the same three questions: whose income counts, how much of that income the children should share, and which costs are added or credited afterward. Knowing which model your state uses makes the official worksheet much easier to follow.
The federal rule behind every state guideline
Federal law requires each state to adopt one set of child-support guidelines and to make them available to everyone in the state. Under 45 CFR 302.56, a guideline must base the order on the paying parent’s earnings, income and other evidence of ability to pay. It must consider the basic subsistence needs of that parent, address how the child’s health care will be covered, and treat the guideline amount as a rebuttable presumption. A court or agency can order a different amount only with a written finding explaining why the guideline amount would be unjust or inappropriate. Each state must review its guideline at least once every four years.
Those federal requirements are the same everywhere. The formula that satisfies them is not, and that is why a result from one state cannot be reused in another.
The three main guideline models
- Income shares
- Most states use this model. The parents’ incomes are added together, and a statewide schedule gives the basic amount that parents at that combined income typically spend on the number of children in the case. Each parent is responsible for the percentage of that amount that matches their share of the combined income. Alabama, Florida, Georgia, Illinois, Pennsylvania and Virginia are examples.
- Percentage of the paying parent’s income
- A smaller group of states applies a set percentage to the paying parent’s income alone. Texas applies percentages to monthly net resources, Alaska to adjusted annual income, Mississippi to adjusted gross income and Wisconsin to income available for child support. Nevada uses tiered percentages of gross income, and North Dakota uses a table keyed to the paying parent’s net income.
- Melson formula
- Delaware and Montana first set aside a self-support amount for each parent, then fund the children’s primary needs, and then share a further percentage of the remaining income through a standard-of-living adjustment. Hawaii uses a related approach.
A few states use their own formula. California’s Family Code section 4055 is an algebraic formula based on both parents’ net disposable income and the time each parent has the children. New York’s Child Support Standards Act applies a statutory percentage to combined parental income up to a cap that is updated periodically, and the court decides how to treat income above the cap.
A simple income-shares example
Suppose Parent A earns $6,000 a month and Parent B earns $4,000, using the income definition the state requires. Their combined income is $10,000, so Parent A has a 60% share and Parent B a 40% share. If the state schedule shows a basic obligation of $1,500 for one child at that combined income, Parent A’s share is $900 and Parent B’s share is $600. When Parent B has the child most of the time, Parent B’s share is treated as spent directly in that home, and Parent A pays the $900 share. Add-ons such as child care and health insurance are then divided by the same percentages.
| Step | Parent A | Parent B |
|---|---|---|
| Guideline income | $6,000 | $4,000 |
| Share of combined income | 60% | 40% |
| Share of $1,500 basic obligation | $900 | $600 |
The schedule amount in the example is illustrative. Real schedules differ by state, and many are updated after each quadrennial review. Use the calculator for your state, which applies that state’s current published schedule or formula.
What happens after the basic amount
Most worksheets continue past the basic amount. Common later steps are:
- Parenting-time adjustments when the paying parent has the children for a qualifying number of overnights. See how parenting time changes support.
- Child care and health insurance for the children, usually shared in proportion to income. See child care and health insurance in the worksheet.
- Low-income protections, such as a self-support reserve or a minimum order, which federal law requires states to consider.
- Other children a parent is legally required to support. See support for children from other relationships.
- Deviations, where a judge departs from the guideline with written findings.
How this site applies your state’s model
Each state calculator on this site uses the model, schedule, rounding rules and low-income rules published by that state, and it links to the governing source. When your case needs a worksheet branch the calculator does not compute, such as a deviation or an unusual custody arrangement, the calculator stops and tells you which official worksheet line to complete. It does not guess at a number. Our methodology page explains how each state module is tested against official examples before it is published.
Next: find out which income figure your state uses, or choose your state.
Updated October 17, 2026. Published by Kestervale LLC. Educational information, not legal advice. Report a correction.