California
How is child support calculated in California?
Quick answer
California sets child support using a statewide guideline formula written into Family Code § 4055. The formula is applied by the court (and by calculators that implement it), and it’s presumed to be correct — judges depart from it only in specific situations.
Researched by Dan Martin, Legal Researcher · Published by Onbello Legal · Last updated October 2026
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Child support when the kids live with a grandparent or other relative
What the formula looks at
The guideline turns on a handful of core inputs: each parent’s net disposable income, the percentage of time each parent has the children (the “timeshare”), and the number of children. Net income is gross income minus allowable deductions like taxes, mandatory retirement, health insurance premiums, and union dues.
In broad terms, the larger the income gap between the parents and the less time the higher earner spends with the children, the higher their support obligation tends to be. Because timeshare is a direct input, your parenting schedule and your support number are linked.
Why timeshare matters so much
Timeshare is the share of overnights each parent has. A move from, say, a 70/30 schedule to 50/50 can meaningfully change the support figure, because the formula credits the time each parent already spends caring for the children.
That’s why it’s worth seeing what a given parenting schedule actually produces before you negotiate support — the schedule you agree to feeds directly into the number.
Getting an estimate
You can estimate guideline support yourself with the same § 4055 formula the court uses. Our free California child support calculator walks you through the income, deduction, and timeshare inputs and shows what a court would likely order — no account needed.
Keep in mind an estimate is a starting point, not an order. Add-ons like childcare and uninsured medical costs, and any grounds for departing from guideline, can change the final number.
What changed on September 1, 2024 (SB 343)
Senate Bill 343 (Stats. 2023, ch. 213) revised the statewide guideline, and the new version of Family Code § 4055 has been operative since September 1, 2024. It replaced the income bands used to set the K factor in § 4055(b)(3), and it tied the low-income adjustment to full-time minimum wage: a paying parent (the obligor) whose net disposable income is less than the monthly gross income from full-time minimum-wage work is presumed entitled to the adjustment, though the presumption can be rebutted (§ 4055(b)(7)).
SB 343 also changed how add-ons are shared. Childcare costs related to work or job training and reasonable uninsured health care costs, which the court must order under § 4062(a), are now divided in proportion to the parents’ adjusted net incomes under § 4061(a), unless a party asks, or the court decides on its own, to divide them differently. Before September 1, 2024, the default was one-half to each parent.
Tools and resources
Where to check this
Forms, deadlines, and local rules change. Verify anything on this page against the official self-help resources for your state before you rely on it.
This page is general legal information, not legal advice, and does not create an attorney–client relationship. Laws and local rules vary and change. For advice about your situation, consult a licensed family-law attorney in your state.
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