How do I calculate child support?

Parental Income: Courts consider both parents' gross income from all sources:

• Wages, salaries, commissions, and bonuses
• Self-employment income (after business expenses)
• Rental property income
• Investment income and dividends
• Unemployment or disability benefits
• Social Security benefits (in some states)
• Overtime pay (if regular and consistent)

Excluded or Adjusted Income: Some income may be excluded, including child support received for children from other relationships, spousal support paid or received, and imputed income if parent is voluntarily unemployed. Income from new spouse is generally not included.

Number of Children: Support amount increases with number of children. Different percentages apply for 1, 2, 3+ children. Some states use flat percentages; others use income shares models that vary by income level.

Time-Sharing Percentage: Custody arrangement affects support. More equal time-sharing reduces support obligation. Thresholds vary (some states adjust at 20%, others at 35%).

Income Shares Model (majority of states): Based on principle that child should receive same proportion of parental income as if family were intact. Combines both parents' incomes, refers to guideline schedule, prorates obligation between parents based on income percentage, and adjusts for time-sharing.

Percentage of Income Model: Support is flat percentage of non-custodial parent's income. Texas uses this model (20% for 1 child, 25% for 2, 30% for 3). Wisconsin also uses this model. Simpler calculation but less precise for shared custody.

Melson Formula (Delaware, Hawaii, Montana): Ensures basic needs of parents met before calculating support. Subtracts self-support reserves from income and allocates remaining income proportionally.

Health Insurance: Support order typically addresses which parent provides coverage, cost of children's portion of premiums, and how uncovered medical expenses are split (often 50/50 or proportional to income).

Childcare Costs: Work-related childcare usually added to base support, including after-school care, summer camp, and daycare. Typically split proportionally to income.

Educational Expenses: Some states include private school tuition (if historically provided), extracurricular activities, school supplies and fees, and college expenses (in some jurisdictions).

Most states provide downloadable PDF worksheets with instructions, online calculators on court websites, built-in calculators in e-filing systems, and mobile apps (some states).

Required Information to complete calculations:

• Both parents' gross monthly income
• Number of children from this relationship
• Percentage of time children spend with each parent
• Health insurance costs for children
• Childcare costs
• Other children each parent supports

Courts can deviate from guideline amounts if specific circumstances justify it:

• Child has special needs requiring extraordinary expenses
• Parent has unusually high or low income
• Child has significant assets or income
• Parent has extraordinary travel costs for visitation
• Parent has significant debt from marital obligations
• Guideline amount would be unjust or inappropriate

Any deviation must be explained in writing by the court and must serve the child's best interests.

Support can be modified when circumstances change substantially:

• Significant income change (15-20% threshold in many states)
• Change in custody or time-sharing arrangement
• Child's needs change (medical, educational)
• Change in childcare or health insurance costs
• Automatic review every 3 years (in some states)

Either parent can request a modification by filing a motion with the court and demonstrating the changed circumstances.