How Is Child Support Calculated?
The three U.S. guideline models explained — Income Shares, Percentage of Income, and the Melson Formula — and the inputs that move the number.
Although every state writes its own worksheet, almost all of them fall into one of three models. Knowing your state’s model is the single biggest predictor of how your number is computed.
1. Income Shares (41 states + D.C.)
Both parents’ incomes are added together, matched to a “schedule” of basic support for the number of children, and then each parent pays their proportional share. Child care and health insurance are added on top, and significant parenting time can trigger a credit. Deep dive: Income Shares
2. Percentage of Income (6 states)
A flat (or graduated) percentage of only the paying parent’s income. Simple and predictable. Texas, Wisconsin, Alaska, Mississippi, Nevada, and North Dakota use this. Deep dive: Percentage model
3. Melson Formula (Delaware, Hawaii, Montana)
Income Shares plus a protected self-support reserve for each parent and a standard-of-living adjustment for the child. Deep dive: Melson Formula
The inputs that move the number
- Number of children — obligations rise, usually at a decreasing rate
- Parenting time (overnights) — ~40%+ often reduces the base in Income Shares states
- Child care & health insurance — typically split by income, on top of the basic obligation
- Existing orders for other children — many states deduct support already paid