How SupportSum calculates child support

Every state sets its own child support guidelines by law, and those guidelines define the formula courts use. SupportSum's calculators are built from each state's official published guidelines. We do not invent numbers or apply a single national formula.

The three models we implement

Income Shares (used by most states)

Combines both parents' incomes, finds the total support obligation from the state's schedule, and divides it in proportion to each parent's share of income. This model is based on the idea that children should receive the same proportion of parental income they would have received if the family were intact.

Percentage of Income (TX, MS, WI, AK, ND)

Applies a set percentage of the paying parent's income, based on the number of children. Only the non-custodial parent's income is used in the base calculation. This model is simpler but does not account for the other parent's earnings.

Melson Formula (DE, HI, MT)

An income-shares variant that also accounts for each parent's basic needs before allocating support. It first subtracts a self-support allowance, then calculates the child's primary needs, and finally applies a standard of living adjustment to remaining income.

Sources and updates

On every state page we link to the official source we used, typically the state's judicial branch, child support services agency, or statutory guideline schedule. We show a "last updated" date and review the guidelines for changes over time.

How we verify our data

  1. We locate the official child support guideline or statute for each state
  2. We extract the schedule tables, percentages, or formula parameters from the official source
  3. We implement the calculation in code and test against known examples
  4. We link to the official source on every state page so you can verify independently
  5. We display a "last verified" date and revisit periodically for updates

How calculations run

All calculations happen in your browser. When you enter income figures and press Calculate, the math runs locally on your device using JavaScript. No data is sent to our servers. This protects your privacy and means our estimates are instant.

Limitations

Our results are estimates. Courts have discretion and may adjust the amount based on factors a calculator cannot capture, including:

  • Childcare costs and who pays them
  • Health insurance premiums for the children
  • Special needs or extraordinary medical expenses
  • Shared-custody or split-custody arrangements
  • Additional children from other relationships
  • Deviations the judge considers appropriate

Always confirm your situation with a licensed family law attorney in your state.

Try our calculators

Free estimates for all 50 states, based on official guidelines.

View All State Calculators