Child Support Calculator

Q: What is the income shares model for child support?

The income shares model estimates what both parents would have spent on the children if the household had stayed intact, then divides that obligation between the parents in proportion to each one's share of combined income. The parent with less parenting time generally pays their proportional share to the other parent. About 40 states use this approach.

Q: Does 50/50 custody eliminate child support?

Not usually. Even with equal parenting time, the higher-earning parent typically still owes some support because the income shares model keeps the children's standard of living consistent across both homes. Equal time reduces the payment but rarely zeroes it out when incomes differ.

Q: Can a child support order be changed later?

Yes. Either parent can request a modification when there is a substantial change in circumstances such as a job loss, a significant raise, a change in custody, or new childcare or medical costs. Many states also allow periodic review every few years.

Estimate monthly child support payments using the income shares model, the framework used in roughly 40 U.S. states. The calculator combines both parents' gross monthly income, applies a basic support obligation based on the number of children, adds healthcare and childcare costs, and assigns each parent a share proportional to their income — with an adjustment for shared custody time.

Family & Income Information

State For reference. This calculator uses a generic income-shares formula.

Number of children

Parent 1 gross monthly income ($)

Parent 2 gross monthly income ($)

Parent 1 custody time (%)

50%

Monthly healthcare costs ($) Premiums and uninsured medical for the children.

Monthly childcare costs ($) Work-related daycare, after-school care.

Legal Disclaimer: Child support calculations vary significantly by state. Many jurisdictions adjust for self-support reserves, prior-order support, extraordinary medical or educational expenses, and high-income deviations. This calculator uses a simplified income-shares formula and does not substitute for your state's official worksheet. Verify with your state's child support guidelines or a family law attorney.

How This Calculator Works

This calculator applies the income shares model, the framework used in roughly 40 states. The math runs in four steps. First it adds both parents' gross monthly incomes to get combined income. Second, it applies a basic obligation percentage tied to the number of children — this model uses about 17% of combined income for one child, 25% for two, 29% for three, and rising from there, reflecting the economies of scale that real state schedules build in.

Third, it adds healthcare premiums and work-related childcare to that basic obligation to get the total obligation. Fourth, it assigns each parent a share of that total in proportion to their income, then applies a shared-parenting adjustment: as the paying parent's overnight time approaches 50%, the payment is reduced by up to half. The parent with the majority of overnights receives support from the other parent.

A Worked Example

Two parents have two children. Parent 1 earns $6,000 per month and Parent 2 earns $4,000, with Parent 1 having the children 60% of overnights. Monthly healthcare is $200 and childcare is $800.

Step 1 — Combined income: $6,000 + $4,000 = $10,000.

Step 2 — Basic obligation for two children: 25% × $10,000 = $2,500.

Step 3 — Total obligation: $2,500 + $200 + $800 = $3,500.

Step 4 — Parent 2 is the payer (less custody time) and earns 40% of combined income, so their share is 0.40 × $3,500 = $1,400. Their custody time is 40%, so the shared-parenting adjustment reduces the payment by 0.40 × 0.5 = 20%, giving a final estimate of about $1,120 per month. Your state's official worksheet may land somewhere different.

What Affects Your Child Support Payment

Which model your state uses. Income shares (about 40 states), percentage-of-obligor-income (roughly a dozen), and the Melson formula (a few) can produce meaningfully different numbers from the same inputs.
The custody/overnight split. More equal parenting time generally lowers the higher earner's payment, but the exact threshold and formula vary by state.
Add-on expenses. Health insurance premiums, uninsured medical, and work-related daycare are usually shared in proportion to income and can move the total significantly.
Self-support reserve and low-income adjustments. Many states protect a minimum amount of the paying parent's income, reducing support for lower earners.
Other children and prior orders. Support already paid for children from another relationship is commonly deducted before the formula runs.
High-income and deviation rules. Above a certain combined income, courts may cap or adjust the schedule, and judges can deviate for extraordinary needs.

Frequently Asked Questions

What is the income shares model for child support?

It estimates what both parents would have spent on the children if the household had stayed intact, then divides that obligation between them in proportion to each parent's share of combined income. The parent with less parenting time generally pays their proportional share to the other parent.

Does 50/50 custody eliminate child support?

Not usually. Even with equal parenting time the higher-earning parent typically still owes some support, because the model keeps the children's standard of living consistent across both homes. Equal time reduces the payment but rarely zeroes it out when incomes differ.

Is child support based on gross or net income?

Most income shares states start from gross monthly income, though some allow deductions for taxes, mandatory retirement, union dues, or support paid for other children. This calculator uses gross income; your state's worksheet may apply specific adjustments.

Can a child support order be changed later?

Yes. Either parent can request a modification after a substantial change in circumstances — a job loss, a significant raise, a change in custody, or new childcare or medical costs. Many states also allow periodic review every few years.

The Income Shares Model

Under the income shares model, courts estimate what the parents would have spent on the children if the family remained intact, then divide that total obligation between the parents in proportion to each parent's income. The non-custodial parent typically pays their share to the custodial parent. When parenting time is roughly equal, many states apply a shared-custody adjustment that reduces the payment.

About a dozen states use a different framework called the percentage of obligor income model, which calculates support solely from the paying parent's income. A handful of states use the Melson formula. Always check your state's specific approach.