New Hampshire Child Support Calculator

At $6,000 per month in combined monthly gross income, New Hampshire's guidelines produce roughly $707/month for 1 child, $978/month for 2 children, $1,172/month for 3 children, $1,252/month for 4 children. These figures come from running New Hampshire's own guideline formula, but they hold several things constant -- assumes the obligor has 65% of the combined income shown (paid monthly), sole-custody parenting category, and no deductions or existing obligations entered. Your actual number depends on both parents' incomes, your parenting-time schedule, and add-on costs like childcare and health insurance, so run the calculator for your own case.

New Hampshire uses the Percentage of Combined Net Income model. New Hampshire applies a statutory percentage table to the parents' combined ANNUAL net income, interpolating linearly between the table's breakpoints. A self-support reserve protects a minimum standard of living for the paying parent before support is owed.

New Hampshire's guideline runs on combined net income (annual table, both parents). That distinction matters: entering gross income into a formula built on net income (or the reverse) produces a materially wrong figure. Most states count income from essentially any regular source -- wages, self-employment, bonuses, commissions, rental and investment income, and many benefits -- not just salary.

Not necessarily. New Hampshire's guideline weighs each parent's share of combined income alongside the parenting-time arrangement, so a significantly higher earner can still owe support even at an even split of time.

This calculator's core formula has been verified against the primary source, with any unimplemented rules listed openly rather than hidden. It implements the guideline in effect as of 2025-01-01, and a human last checked it against the primary source on 2026-08-12. Sources: RSA 458-C:2 (definitions, incl. net income and self-support reserve); RSA 458-C:3 (child support formula and percentage table). It is still an estimate, not a court order -- a judge can order a different amount, and this is not legal advice.

The New Hampshire guideline this calculator implements took legal effect on 2025-01-01. States revise their guidelines periodically -- federal rules require each state to review its guidelines at least once every four years -- so a figure from an older calculator or article may reflect a superseded rule.

Federal income tax is estimated with 2025 single-filer brackets rather than the exact DHHS-published withholding table for 'a single person who has claimed a withholding allowance for 2 people' (RSA 458-C:2, VI), which was not accessible (dhhs.nh.gov blocked automated fetches). Results may differ from the official worksheet. Does not collect the RSA 458-C:2, I(b)-(d) deductions for self-employment tax, mandatory retirement contributions, or state income tax paid. If any of these apply to your case, treat the estimate as a starting point and confirm the figure with an attorney, a mediator, or New Hampshire's official worksheet.

Yes. The figure produced by New Hampshire's Percentage of Combined Net Income guideline is presumptive, not mandatory: a court can order a different amount when applying the guideline would be unjust or inappropriate for the specific case, and generally must state its reason on the record. Common grounds include extraordinary medical or educational expenses, a child's special needs, or costs the formula does not capture. New Hampshire's guideline is set out in RSA 458-C:2 (definitions, incl. net income and self-support reserve).

You have to file for a modification -- a change in your circumstances does not change what you owe on its own. New Hampshire, like most states, requires a substantial change in circumstances: a significant involuntary income change, a change in the parenting schedule, or a material change in the child's needs. Until a court or the state child support agency issues a new order, the existing amount stays fully enforceable and arrears keep accruing, and a modification is generally not applied retroactively before the date you filed -- so filing promptly matters.