California child support calculator

Most states publish a table; California publishes an equation. Family Code § 4055 defines the statewide uniform guideline as CS = K[HN − (H%)(TN)], where HN is the higher earner's net monthly disposable income, TN is both parents' combined net disposable income, H% is the approximate share of time the higher earner has primary physical responsibility for the children, and K is the fraction of combined income the legislature allocates to child support. The result is the one-child amount; § 4055(b)(4) multiplies it for additional children. If the result is positive, the higher earner pays it; if negative — which happens when the higher earner also has most of the parenting time — the lower earner pays the absolute value (§ 4055(b)(5)).

"Net disposable income" is where the real work lives. Under § 4059 it means gross income minus the taxes actually payable for the parent's true filing status, FICA, mandatory union dues and retirement required by the job, health insurance premiums for the parent and the children they must support, state disability insurance, court-ordered child or spousal support actually paid for others, and — at the court's discretion — job-related expenses and hardship deductions. Computing actual tax liability is why California courts run certified software and why the state's official guideline calculator asks for your full tax picture. This calculator takes each parent's net disposable income directly: the formula is exact; the net-income step is yours, the conversion table's, or the official calculator's.

K is built in two moves. First, a fraction of combined income is read from the statute's schedule — five bands since September 1, 2024, when SB 343 and AB 1755 replaced the four bands that had stood since the 1990s. Second, that fraction is scaled by time-share: multiplied by (1 + H%) when the higher earner has half the time or less, or (2 − H%) when they have more. The statute's own example: at $1,000 combined net and 20% time-share, K = (1 + 0.20) × (0.165 + 1,000/82,857) = 0.21 — a figure this calculator reproduces exactly, as a test.

When the paying parent's net disposable income is below what full-time minimum-wage work grosses in a month — $16.90/hour in 2026 × 40 hours × 52 weeks ÷ 12 = $2,929.33 — § 4055(b)(7) presumes the payer is entitled to a reduction. The statute caps the reduction: support may be lowered by at most CS × ($2,929.33 − payer's net) ÷ $2,929.33. That defines a range, from the fully-adjusted floor up to the unadjusted formula amount, and § 4055(c) requires any computer program calculating support to display that range rather than pick a point. This calculator does exactly that — and separately, § 4057(b)(5) lets a court trim an order that would still exceed half the payer's net income after adjustment; the calculator flags that too.

On top of the formula amount, § 4062 makes two additions mandatory when the costs are actually incurred: employment-related child care (including education or training for job skills) and the children's reasonable uninsured health care costs. Since September 2024, § 4061 divides these in proportion to the parents' net disposable incomes by default — the old one-half-each rule is gone — and with a wrinkle: for the proration only, the paying parent's net income is first reduced by the base support they pay (§ 4061(d)). The receiving parent's income is not increased by it. This calculator applies exactly that mechanic and shows the shares. One caution: the health insurance premium is not an add-on — it is a § 4059 deduction already inside net disposable income. Only uninsured costs are added here; entering the premium too would double-count it.

At the top, there is no income cap: the K fraction simply declines as income rises, and § 4057(b)(3) lets an extraordinarily-high-income parent rebut the presumption where the formula exceeds the children's needs. At equal incomes and equal time the formula nets to zero — but only then; 50/50 custody with unequal incomes still produces support. In default proceedings, § 4055(b)(6) sets H% to 0 or 100 by rule. And for more than one child, § 4055(b)(8) allocates the total so the youngest child's share equals the one-child amount, the next child's share is the increment to the two-child amount, and so on — the work panel shows this allocation, since it matters when support for an older child ends.

Parent A nets $6,500 a month; Parent B nets $3,500; two children; Parent A has 146 overnights (40% of the year); Parent B pays $500 a month in work-related child care. Combined net income TN is $10,000, which sits in the flat 0.250 band. Parent A is the higher earner with 40% time-share, so K = (1 + 0.40) × 0.250 = 0.35. One child: 0.35 × ($6,500 − 0.40 × $10,000) = 0.35 × $2,500 = $875. Two children: $875 × 1.6 = $1,400, positive, so the higher earner — Parent A — pays. For the child care, § 4061(d) first reduces A's net by the $1,400 base: shares become $5,100 : $3,500, so A owes 59.3% of the $500 — $296.51 — on top. Total: $1,696.51 a month, about $20,358 a year. Every step appears, cited, in the calculator's work panel.