New Hampshire child support calculator

New Hampshire uses a percentage-of-income formula. Both parents’ net monthly income is combined, and a single guideline percentage — set by RSA 458-C:3 and graduated by income level and the number of children — is applied to the combined income to give the total obligation. Each parent is responsible for the share that matches their percentage of the combined income; the noncustodial parent pays their share to the other.

The heart of the calculation is the percentage table in RSA 458-C:3, I(a). For one child the percentage of combined net income runs from 25.6% at $15,000 or less of annual combined net income down to 19% at $125,000 or more; two children run 35.5% → 26%; three children 42.5% → 31%; four or more 45% → 33.5%. Between the listed income levels the percentage is interpolated, and the DHHS publishes the resulting schedule in $1,000 income increments.

New Hampshire orders a medical support obligation presumptively equal to 4% of each parent’s gross income (RSA 458-C:3, V), and the obligee’s allowable child-care and medical costs are handled by deducting them from that parent’s income before the share split (RSA 458-C:3, II). A self-support reserve — $1,729/month for 2026 — protects low-income paying parents: if support would drop the payer below it, the order is capped at the difference or set to a minimum support order (RSA 458-C:3, IV).

New Hampshire’s formula does not build in a parenting-time discount the way some states do; instead a court may deviate from the guideline amount for the reasons listed in RSA 458-C:5 — including equal or near-equal parenting time, the economic consequences of the split, and extraordinary expenses — on a written finding. This calculator computes the standard guideline obligation before any deviation.

It combines both parents’ net income, applies the RSA 458-C:3 guideline percentage, and splits the total by income share. It does not compute net income from your pay stubs, add the 4% medical support obligation, run the obligee child-care/medical deduction, apply the self-support reserve cap in detail, or apply a deviation the court may order. For a figure you can file, use the official New Hampshire worksheet or consult an attorney.