How to Calculate Child Support

What is Child Support?

A child support calculator estimates monthly payments using the income shares model, which bases the obligation on both parents’ combined income and the proportion each contributes. Most US states use this approach to ensure the child receives the same share of parental income they would have if the household were intact.

Formula

Each Parent’s Obligation = (Parent Income / Combined Income) × Basic Support Obligation – Credits

I_a: Parent A Income ($/month) — Gross or net monthly income of the paying parent
I_b: Parent B Income ($/month) — Gross or net monthly income of the receiving parent
BSO: Basic Support Obligation ($/month) — Amount from the state guideline schedule for combined income and number of children
C: Credits ($/month) — Deductions for health insurance, childcare, and parenting time

Step-by-Step Guide

1Determine each parent’s gross or net monthly income (varies by state)
2Combine both incomes and look up the Basic Support Obligation from the state guideline table
3Divide the obligation proportionally based on each parent’s share of combined income
4Apply adjustments for healthcare premiums, childcare costs, and parenting time credits

Worked Examples

Input

Parent A earns $5,000/mo, Parent B earns $3,000/mo, one child

Result

Combined $8,000 → guideline obligation ~$1,100. Parent A owes 62.5% = $687.50/mo

Input

Combined income $12,000/mo, two children, Parent A earns 70%

Result

Guideline ~$1,800. Parent A share = $1,260/mo before credits

Common Mistakes to Avoid

✕Using gross income when the state requires net income (or vice versa)
✕Forgetting to include overtime, bonuses, and self-employment income
✕Not adjusting for the number of overnights each parent has

Frequently Asked Questions

Does child support cover college tuition?

In most states, child support ends at 18 or high school graduation. A few states (like New York and New Jersey) can order support through college under certain conditions.

Can child support be modified?

Yes. Either parent can petition for modification when there is a substantial change in circumstances, such as a job loss, significant raise, or change in custody arrangement.

Is child support taxable?

No. Child support payments are not taxable income to the recipient and not deductible by the payer under current federal tax law.

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