There is no national child support formula. Every state sets its own, and the differences are not small — the same two incomes can produce very different orders depending on whether your state counts both parents' earnings or only the paying parent's. Start with your state below.
Ohio uses the income-shares model: both parents' incomes count, and the schedule reflects what two parents at that combined income would ordinarily spend on their children.
Texas uses the percentage-of-obligor model: a set percentage of the paying parent's monthly net resources, with no reference to what the other parent earns.
Florida uses the income-shares model, with the guidelines schedule written directly into Fla. Stat. 61.30 rather than published separately by an agency.
Indiana uses the income-shares model on a weekly basis, with schedules issued by the Indiana Supreme Court rather than by statute.
More states are being added. Rather than publish a formula we haven't verified against the statute, every state below shows how its guideline works and links to the law — and gets a calculator once we've tested it against the state's own figures.
Almost every state uses one of three standard models, plus a few with formulas of their own. Knowing which one applies tells you immediately whether the other parent's income affects your number.
Both parents' incomes are added together, looked up on a state schedule that estimates what a two-parent household at that income spends on children, and then split between the parents in proportion to what each earns. The paying parent hands over their share. Used by the large majority of states.
Only the paying parent's income matters. A flat percentage is applied to it, rising with the number of children — the receiving parent's earnings are usually irrelevant. Simpler and more predictable, but it ignores a large disparity in the other direction.
An income-shares variant that first sets aside a self-support reserve for each parent, then covers the children's basic needs, then adds a share of any income left over so the children's standard of living tracks the parents'. Used by only three states.
A handful of states use a formula that doesn't fit the standard buckets — California's guideline, for instance, folds the parenting-time percentage directly into the algebra rather than applying it as an adjustment afterwards.
Kidtime tracks every overnight, swap and handover as it happens, which is what turns a parenting-time percentage into something you can show a court. Free to start.
Each row is that state's guideline model and the rule that governs it, with the statutory citation. Where a calculator is live it is linked; otherwise the state custody guide is.
income-shares (both parents' combined gross income), Rule 32 Ala. R. Jud. Admin.
percent-of-adjusted-income of the obligor under Alaska Civil Rule 90.3(a); shared-custody cross-credit once EACH parent has the child ≥30% of overnights (Civ. R. 90.3(b))
income-shares — both parents' incomes → Schedule of Basic Support Obligations, with a parenting-time day adjustment (ARS 25-320 + AZ Child Support Guidelines)
income-shares — combines both parents' incomes against the Family Support Chart (Admin. Order No. 10, eff. 2020-07-01)
statewide uniform guideline formula incorporating BOTH incomes + timeshare % (Fam. Code 4055; 'DissoMaster')
income-shares — combine both parents' adjusted gross incomes, read the schedule of basic obligations, apportion by each parent's income share, adjust for overnights/health-insurance/child-care (C.R.S. 14-10-115); schedule extended to combined $40,000/mo eff. 3/1/2026
income-shares (both parents' combined net weekly income; guidelines set by the Commission per 46b-215a; regs 46b-215a-1 et seq.)
melson — Delaware is the origin state of the Melson formula (an income-shares variant that reserves each parent's self-support allowance before a percentage Standard-of-Living Adjustment); rebuttable presumption (Del. Fam. Ct. Civ. R. 501–509; 13 Del. C. § 514)
income shares — both parents' incomes + Schedule of Basic Child Support Obligations; shared-custody adjustment (x1.5) when a parent has 35%+ of the time (DC Code 16-916.01)
income-shares — both parents' net incomes on the statutory schedule, apportioned by income share, with a 1.5x gross-up once a parent exercises >=20% of overnights (Fla. Stat. 61.30)
income-shares — both parents' incomes → basic obligation table; SB454 rewrite effective 1/1/2026 adds a MANDATORY parenting-time adjustment (overnights^2.5) and raises the cap to $40k/mo combined (O.C.G.A. 19-6-15)
Melson formula — one of only ~3 states; guidelines set/updated by the Family Court under HRS 576D-7 (both incomes, each parent's + child's needs, then share of surplus)
income-shares — combined parental gross income, proportional share (Idaho Code 32-706 + Idaho Child Support Guidelines, IRFLP Rule 120); $50/mo/child rebuttable minimum
income-shares — both parents' net incomes + parenting-time overnights; since 7/1/2017 (750 ILCS 5/505)
income-shares; combines both parents' WEEKLY adjusted income against the Guideline Schedules, with a parenting-time credit scaled to the non-custodial parent's annual overnights (Ind. Child Support Guidelines; IC 31-16-6-1)
income-shares (combines BOTH parents' net monthly incomes; Iowa Ct. R. ch. 9)
income-shares — combined domestic gross income; Kansas Child Support Guidelines (Sup. Ct. Admin. Order 2025-RL-121, eff. 7/1/2025; authority K.S.A. 20-165)
income-shares (both parents' incomes; KRS 403.212) WITH a graduated shared-parenting-time credit / adjustment (KRS 403.2121, eff. 2023)
income-shares (both parents' incomes + a statutory schedule; La. R.S. 9:315 et seq.)
income shares — both parents' incomes → statutory child support table (19-A §2006, ch. 63; ~$400k combined-income cap)
income-shares (both parents' adjusted actual incomes; Fam. Law 12-201 et seq., 12-204)
guideline-formula — MA Child Support Guidelines (rebuttable presumption; both parents' combined available income, income-shares hybrid), authorized by c. 208 §28
income-shares — Michigan Child Support Formula (MCSF), based on both parents' net resources + parenting-time overnights + child-care and health-care costs (MCL 552.519(3), 552.605)
income shares — combined parental income (PICS) with a parenting-expense adjustment tied to court-ordered parenting time (Minn. Stat. 518A.34, 518A.35)
percent-of-obligor adjusted gross income: 14% one child, 20/22/24/26% for 2/3/4/5+ (§ 43-19-101)
income-shares via Supreme Court Rule 88.01 + Civil Procedure Form 14; guideline amount is a rebuttable presumption (452.340.8–.9)
Melson formula — both parents' incomes + a primary/personal-needs allowance + standard-of-living adjustment (Admin. R. Mont. 37.62.101 et seq., adopted under 40-4-204 / 40-5-209). One of only three Melson states.
income-shares — combined parental income, guidelines set by Neb. Supreme Court rule as a rebuttable presumption (Neb. Rev. Stat. 42-364.16; Neb. Ct. R. ch. 4, art. 2)
percent-of-obligor gross income, tiered (16%/8%/4% for one child), set by regulation NAC 425; joint-physical custody uses an offset of each parent's calculated obligation
combined-income percentage guideline — total obligation = both parents' combined net income x a guideline % (declining as income rises), then prorated by each parent's income share (RSA 458-C:3)
income-shares (combined parental income + overnights); N.J. Ct. R. 5:6A + Child Support Guidelines, Appendix IX (Sole-Parenting Worksheet IX-C, Shared-Parenting Worksheet IX-D)
income-shares — combined parental income; Worksheet A (basic visitation) vs Worksheet B (shared responsibility, obligation x1.5) split at 35% of the year / ~128 overnights (NMSA 40-4-11.1)
income-shares (CSSA): % of COMBINED parental income, prorated pro rata — 17% one child / 25% two / 29% three / 31% four / 35%+ five (DRL 240(1-b); FCA 413)
income-shares — presumptive statewide NC Child Support Guidelines prescribed by the Conference of Chief District Judges (G.S. 50-13.4(c)/(c1))
percent-of-obligor net income — obligor's income only; obligee's income counts only if ≥3x the obligor's (14-09-09.7); guideline detail in N.D. Admin. Code 75-02-04.1
income-shares — combined-income basic child support schedule (ORC 3119.021), with a 10% parenting-time adjustment at 90+ overnights (ORC 3119.051)
income-shares — combined-income Schedule of Basic Child Support Obligations, each parent's share pro-rata to income (43 O.S. §§ 118, 119)
income-shares — both parents' incomes shared in proportion (ORS 25.275); formula + parenting-time/overnight credit set by rule (OAR ch. 137, div. 50)
income-shares — combined net income of both parents (23 Pa.C.S. 4322; Pa.R.C.P. 1910.16-1)
income-shares — RI Family Court guidelines adopted by administrative order under R.I. Gen. Laws 15-5-16.2
income shares — rebuttable presumption the guideline amount is correct (63-17-470; SC Child Support Guidelines, S.C. Code Regs. 114-4710)
income-shares — combined-net-income schedule, obligor pays proportionate share (SDCL 25-7-6.2); shared-parenting cross credit at 180+ overnights each (25-7-6.27)
income shares — both parents' incomes + number of days with each parent; DHS guidelines are a rebuttable presumption (TCA 36-5-101(e); DHS Rules ch. 1240-02-04)
percent-of-obligor net resources (20% one child, +5%/child; Fam. Code 154.125)
income-shares — both parents' incomes combined against a base child-support obligation table (Utah Code Title 81, ch. 6; e.g. 81-6-205)
income-shares (both parents' available incomes; 15 V.S.A. §§ 654, 656) with a shared/split-custody adjustment once each parent has 30%+ overnights (§ 657)
income-shares — combined-gross-income Schedule of Basic Child Support Obligation, divided by each parent's income share (Va. Code § 20-108.2)
income-shares — economic table on the parents' combined monthly net income, presumptive up to $50k/mo (RCW 26.19.020)
income-shares (combined-income basic-obligation table; W. Va. Code 48-13-301)
percent-of-obligor 'percentage of income' standard set by DCF, WITH a shared-placement offset when each parent has 25%+ of overnights (Wis. Stat. 767.511; ch. DCF 150)
income-shares — combined net income of both parents against a statutory table, obligation prorated by each parent's net-income share (W.S. 20-2-304)
This page is general information, not legal advice, and guideline formulas change. Every state summary carries its statutory citation so you can read the controlling text; consult a licensed family-law attorney in your state about your own situation.