FINANCIAL · CHILD SUPPORT
Child Support Calculator
Estimate monthly child support using the Income Shares Model — enter both parents' gross incomes, number of children, and add-on costs for a US-national approximation. Results are educational, not legal advice.
About This Calculator
Get a quick estimate of monthly child support using the Income Shares Model — the framework used by most US states. Enter both parents' gross incomes and the number of children to see the combined basic support obligation and each parent's proportional share. Note: every state has its own guidelines, and this tool provides a US-national approximation for educational purposes only.
How It Works
The Income Shares Model starts with the combined gross monthly income of both parents and applies a support percentage that increases with the number of children (1 child = 17%, 2 = 25%, 3 = 29%, 4 = 31%, 5 = 32%, 6+ = 33%). Each parent's share of the combined basic support is then proportional to their income share. Add-on expenses (child care, medical, extracurricular) are split in the same ratio. The obligor (paying parent) owes their proportional share of both basic support and add-ons.
The Formula
Monthly Payment = (Combined Income × ISM%) × (Obligor Income / Combined Income) + Add-ons × Obligor share
- ISM%
- Income Shares Model percentage: 17% (1 child), 25% (2), 29% (3), 31% (4), 32% (5), 33% (6+)
- Obligor Share
- Obligor income divided by combined parental income
- Add-ons
- Monthly child care + medical + extracurricular costs
Frequently Asked Questions
- Is this calculator accurate for my state?
- This calculator uses a US-national Income Shares approximation and is meant for educational and planning purposes only. Every state in the US has its own child support guidelines with different income definitions, deviation factors, parenting time adjustments, and add-on rules. Do not use this estimate in place of a state-specific calculation, attorney advice, or a court determination.
- What is the Income Shares Model?
- The Income Shares Model (ISM) is a child support guideline framework used by a majority of US states. It is based on the principle that a child should receive the same proportion of each parent's income they would have received if the parents lived together. The model combines both parents' incomes to determine a basic support obligation, then apportions it between the parents proportionally.
- What is the difference between the obligor and obligee?
- In child support, the obligor is the parent ordered to pay support (usually the non-custodial parent), and the obligee is the parent receiving support (usually the custodial parent). Courts determine who is the obligor and obligee based on custody arrangements, parenting time, and incomes.
- What are add-on costs?
- Add-ons are specific expenses beyond basic support that courts may require both parents to share proportionally. Common add-ons include work-related child care, extraordinary medical or dental costs not covered by insurance, and extracurricular activities. Not all states treat the same items as add-ons — check your state's guidelines.
- Does parenting time affect child support?
- Yes, in many states. Shared custody or extended parenting time by the obligor often reduces the support obligation because the non-custodial parent is directly bearing more costs. This calculator does not include a parenting time adjustment — another reason state-specific tools and legal counsel matter.
- What if one parent has no income?
- When one parent has zero reported income, the calculator assigns 100% of the basic support obligation to the other parent. In practice, courts often impute income (assign a presumed earning capacity) to a parent who is voluntarily unemployed or underemployed. This calculator uses actual entered incomes only.