Understanding Child Support Calculations

How They Calculate What You Owe

Child support isn't arbitrary. Every state uses a formula. Understanding that formula is the first step to knowing whether your amount is fair and when you can request a change.

The Two Models

Income Shares Model (Majority of States)

Both parents' income is combined to estimate what the child would receive in an intact household. Support is then divided proportionally based on each parent's share of total income.

Example: If you earn 60% of the combined income, you'd be responsible for approximately 60% of the child support obligation.

Percentage of Income Model (Fewer States)

Support is calculated as a flat percentage of the noncustodial parent's income. Typically:

1 child: 17–25% of income
2 children: 25–35%
3 children: 29–40%

Factors in the Calculation

Regardless of the model, most states consider:

Gross income: Both parents' total income from all sources
Number of children: More children = higher support
Parenting time percentage: More overnight time with you typically = lower support
Healthcare costs: Insurance premiums and out-of-pocket medical expenses
Childcare costs: Daycare, after-school care, babysitting for work
Other children: Support obligations to children from other relationships
Extraordinary expenses: Special needs, educational costs, travel for visitation

How Parenting Time Affects Support

In most income shares states, the amount of time the child spends with each parent directly affects the calculation. More parenting time generally means lower support because you're paying for the child's expenses directly during your time.

This is one reason why parenting time matters financially as well as personally.

Imputed Income

If the court believes you're voluntarily underemployed or unemployed, it can impute income — assign you earning capacity based on:

Your education and training
Your work history
Available jobs in your area
Your health and ability to work

Imputed income means support is calculated on what you COULD earn, not what you DO earn. This is why documenting a genuine job search is critical after job loss.

Deviation Factors

Courts can deviate from the guideline amount for:

Special needs: Children with medical or developmental needs
Travel costs: If visitation requires significant travel
Educational expenses: Private school, tutoring, extracurricular activities
Shared custody: When parenting time is close to 50/50
High income: Some states cap the income used in calculations

When to Request a Modification

You can request a modification when there's a significant change:

Job loss or income reduction: File immediately (arrears build daily)
Income increase by the other parent: May reduce your obligation
Change in parenting time: More time with you can reduce support
Child ages out: When a child turns 18 or graduates high school
Healthcare cost changes: Significant change in insurance or medical expenses

State Child Support Calculators

Many states offer online calculators to estimate support:

Search [your state] child support calculator
These give estimates — the actual amount is set by the court
Use them to prepare for your hearing and understand the range

For more information on support law in your state: Nolo.com Family Law

Next Steps

Look up your state's child support calculator
Run the numbers with your current income and parenting time
If the calculated amount differs significantly from your current order, consult an attorney
If your circumstances have changed, file for modification promptly
Keep records of all support payments you make