Child Support by State: Calculation Methods & Expectations

Two Major Calculation Models

U.S. states use one of two primary models to calculate child support:

Income Shares Model (41 states):
Based on both parents' combined income and the economic data on what intact families spend on children at that income level. The total child cost is then split proportionally by each parent's income share.

Example: Combined income $120,000. Economic tables show $18,000/year spent on one child at this income. Parent A earns 60% ($72,000), Parent B earns 40% ($48,000). Parent A's basic obligation = $18,000 × 60% = $10,800/year ($900/month).

Percentage of Income Model (9 states):
Applies a flat percentage of the non-custodial parent's income. Simpler but doesn't account for the custodial parent's income.

Example (Wisconsin): One child = 17% of gross income. Non-custodial parent earns $60,000. Support = $60,000 × 17% = $10,200/year ($850/month).

Factors That Affect the Amount

Beyond the base formula, courts consider:

Number of children — Each additional child increases the obligation, but not linearly. One child might be 17% of income, but three children might be 29% — not 51%.

Custody arrangement — Shared custody (both parents have 35%+ overnights) often reduces support because both parents directly pay child expenses during their parenting time.

Health insurance costs — The cost of adding the child to a parent's health plan is factored in, usually shared proportionally.

Childcare costs — Work-related childcare (daycare) is added to the base obligation and shared between parents.

Extraordinary expenses — Special needs, private school tuition, extracurricular activities may be added by court order.

Income variations — Self-employment income, bonuses, overtime, and imputed income (if a parent is voluntarily underemployed) all affect calculations.

State-by-State Differences

Child support amounts vary significantly because states use different economic tables, income caps, and adjustment factors:

Higher-obligation states (relative to income):
- Massachusetts, Oregon, Hawaii tend to produce higher obligations due to their economic tables reflecting higher child-rearing costs.

Lower-obligation states (relative to income):
- Texas, Mississippi, Tennessee tend to produce lower obligations relative to income.

Notable state rules:
- Texas: Uses percentage of income: 20% for one child (net resources), capped around $9,200/month in net resources.
- California: Uses complex income shares formula with both parents' income, tax filing status, health insurance, and custody time percentage.
- New York: Combined parental income × percentage (17% for one child, 25% for two), then pro-rated by income share. Subject to a cap (~$163,000 combined income for the standard calculation).
- Florida: Income shares model with custody overnight adjustments. Substantial time-sharing (more than 20% overnights) reduces the obligation.

Estimate your state: Child Support Calculator.

Modification and Enforcement

When to request modification:
- Significant income change (typically 15-20%+ increase or decrease)
- Job loss or disability
- Change in custody arrangement
- Child's needs change (medical, educational)
- Original order is 3+ years old (many states allow periodic review)

Enforcement tools:
If a parent fails to pay, the state can:
- Garnish wages (automatic in most states)
- Intercept tax refunds
- Suspend driver's license and professional licenses
- Report to credit bureaus
- Hold in contempt of court (potential jail time)
- Deny or revoke passport

Payment through state agencies: Most states route payments through a State Disbursement Unit (SDU) to create a clear record. This protects both the payer and recipient by documenting every payment.

Duration: Support typically continues until the child turns 18 (19 in some states) or graduates high school, whichever is later. Some states extend to 21 if the child is in college.