What Is Child Support Based On? Factors That Determine Your Payment

The Core Factors in Child Support Calculation

Child support is not an arbitrary number chosen by a judge. Every state uses a specific formula — called child support guidelines — to calculate how much a parent should pay. While the formulas differ from state to state, they all rely on a common set of factors. Understanding these factors helps you predict what your obligation or entitlement might be and prepares you for the process.

The main factors that determine child support are:

• Both parents' incomes
• The number of children
• The custody and visitation arrangement
• Healthcare and insurance costs
• Childcare expenses
• The state's specific calculation model

Let's examine each of these in detail.

Income: The Primary Factor

Income is the single most important factor in calculating child support. Courts look at the gross income of both parents, which includes far more than just salary or wages.

What Counts as Income

For child support purposes, income typically includes:

• Wages and salaries: Your regular pay from employment, including tips, bonuses, and commissions
• Self-employment income: Net business income after reasonable business expenses
• Overtime pay: If it is regular and ongoing, overtime is usually included
• Rental income: Net income from rental properties
• Investment income: Dividends, interest, and capital gains
• Pension and retirement income: Distributions from retirement accounts, Social Security benefits
• Workers' compensation and disability benefits
• Unemployment benefits
• Military pay and allowances: Including housing and food allowances
• Trust income and annuities

Imputed Income

If a parent is voluntarily unemployed or underemployed — meaning they are earning less than they could reasonably earn — the court may impute income. This means the judge assigns an income level based on the parent's earning potential, considering their education, work history, skills, and the local job market. This prevents parents from deliberately reducing their income to lower their child support obligation.

What Does Not Count as Income

Most states exclude certain types of income from child support calculations:

• Means-tested public benefits (TANF, SNAP, SSI)
• Child support received for other children
• Foster care payments
• One-time windfalls (lottery winnings may be an exception)

Number of Children

The number of children covered by the support order directly affects the amount. Support increases with each additional child, but not proportionally. For example, support for two children is typically less than double the amount for one child, because households benefit from economies of scale.

In states using the Percentage of Income model (like Texas), the percentages are clearly defined: 20% of net resources for one child, 25% for two, 30% for three, 35% for four, and 40% for five or more. In Income Shares states, the total support obligation increases with each child according to economic tables that reflect actual spending patterns.

Custody and Visitation Arrangements

The amount of time each parent spends with the child is a major factor. Most states now use the number of overnights as the measure of custody time. The logic is straightforward: when a child is physically with a parent, that parent is directly providing food, housing, and daily care — so they need less (or no) support money for that time.

Sole Custody

When one parent has sole or primary physical custody, the non-custodial parent typically pays the full guideline amount. This is the simplest calculation scenario.

Joint or Shared Custody

In shared custody arrangements, most states reduce the support amount to account for the paying parent's direct expenses during their custody time. The exact reduction depends on the state's approach:

• Overnight-based adjustments: Support decreases incrementally as the paying parent's overnights increase (used in states like Florida and Colorado).
• Cross-calculation method: Each parent's support obligation is calculated separately, then the amounts are offset (used in states like New York).
• Shared custody threshold: Some states only adjust support when the parent reaches a minimum number of overnights (often 90-110 overnights per year).

State Calculation Models

The three main child support calculation models used in the United States produce different results for the same set of facts:

Income Shares Model (~40 states)

The most widely used model. It estimates the total amount parents would spend on their children if living together, then divides that amount proportionally based on each parent's share of combined income. States like Florida, California, New York, and Illinois use this model.

Percentage of Income Model

A simpler model where the non-custodial parent pays a set percentage of their income. Texas is the most well-known example, applying fixed percentages based on the number of children. Some states using this model base the percentage on gross income, others on net income.

Melson Formula

Used by Delaware, Hawaii, and West Virginia, this more complex formula first ensures each parent retains a minimum self-support reserve, then allocates primary support for the child's basic needs, and finally distributes any remaining income proportionally.

Use our free child support calculator to see estimates based on your state's specific formula.

Healthcare and Insurance

Health insurance costs for the child are factored into most child support calculations. The parent who provides health insurance typically receives a credit against their support obligation, or the premium cost is added to the total support obligation before dividing it between the parents.

Unreimbursed medical expenses — co-pays, deductibles, and costs not covered by insurance — are usually split between the parents proportionally based on their incomes. Some orders specify a threshold (such as the first $250 per year) that the custodial parent covers before expenses are shared.

Childcare Expenses

Work-related childcare costs are included in child support calculations in all states. This includes:

• Daycare or preschool
• Before-school and after-school programs
• Summer day camps
• Babysitting while the parent is at work

These costs are typically added to the base support amount and divided between the parents proportionally. The rationale is that childcare enables the parent to work, which benefits the child.

Additional Factors Courts Consider

Beyond the core factors, courts may consider a range of additional circumstances:

• Special needs: Children with disabilities may require higher support to cover therapy, medical equipment, specialized education, and caregiving costs.
• Educational expenses: Private school tuition, tutoring, and educational assessments may be factored in, especially if the child was already attending private school before the separation.
• Extracurricular activities: Costs for sports, music lessons, and other activities may be included, particularly if the child was actively participating before the separation.
• Travel expenses: If parents live far apart, the costs of visitation travel may be allocated between the parents.
• Prior support obligations: If a parent has existing child support orders for children from other relationships, most states deduct those amounts from their available income before calculating new support.
• In-kind contributions: Direct payments for items like school supplies, clothing, or medical bills may be considered, though they generally do not replace the formal support obligation.

Deviations from Guidelines

State guidelines create a presumptive support amount — meaning it is assumed to be correct unless there is a good reason to change it. Courts can deviate from the guideline amount (upward or downward) based on specific circumstances that the formula does not adequately capture.

Common reasons for deviations include:

• Extraordinary medical expenses
• Significant disparity in living standards between households
• A parent's contribution to the child's education beyond what the formula accounts for
• Shared physical custody arrangements that the formula does not handle well
• Seasonal or fluctuating income that makes a fixed monthly amount impractical
• Agreements between the parents (though the court must approve them as being in the child's best interest)

When deviating, the judge must typically explain the reasoning in writing and state why applying the guideline amount would be unjust or inappropriate.

Ready to estimate your child support? Use our free child support calculator to get an instant estimate based on your state's guidelines. For more background, read our guide on what child support is or explore state-specific information.