California Child Support Calculator

California calculates child support using the statewide uniform guideline formula CS = K[HN – (H%)(TN)] under Family Code § 4055. The formula considers both parents' combined net monthly disposable income, the income gap between them, and each parent's percentage of custodial time with the child. Under Family Code § 4057, the resulting amount is presumed correct and courts must order it unless a party proves deviation is justified.

California uses net monthly disposable income as defined in Family Code § 4059, not gross income. Net disposable income includes wages, salary, commissions, bonuses, rental income, Social Security benefits, and self-employment earnings, minus federal and state income taxes, FICA, mandatory retirement contributions, and health insurance premiums. Senate Bill 343, effective September 2025, shifted the K-factor from gross to net income calculations for the first time since 1992.

Custodial timeshare directly impacts California child support through the H% variable in the guideline formula. H% represents the percentage of time the higher-earning parent has primary physical responsibility for the child. Even small changes in timeshare — for example, moving from 20% to 30% — can significantly shift the support amount. When parents have different timeshare arrangements for multiple children, Family Code § 4055 averages the percentages across all children.

California courts can modify child support when there is a material change in circumstances, such as a significant income increase or decrease, job loss, change in custodial timeshare, or new children. Either parent files a motion to modify using Judicial Council Form FL-300. The court recalculates support using the current guideline formula under Family Code § 4055. Modifications take effect from the filing date of the motion, not retroactively.

Family Code § 4062 requires two mandatory add-on expenses beyond base support: childcare costs related to employment or job training, and reasonable uninsured health care costs for the children. Discretionary add-ons under § 4062(b) include educational expenses, special needs costs, and travel expenses for visitation. All add-on expenses are divided in proportion to each parent's net disposable income under Family Code § 4061.

California has no fixed minimum or maximum child support amount — the guideline formula produces the presumed correct figure. However, Family Code § 4055(b)(7) provides a low-income adjustment when the obligor earns below full-time minimum wage, currently $2,929 per month based on California's $16.90 hourly rate effective January 2026. For high earners, Family Code § 4057(b)(3) allows deviation when the formula amount exceeds the children's reasonable needs.

Under Family Code § 3901, California child support continues until the child turns 18, or until age 19 if the child is still a full-time high school student and not self-supporting — whichever comes first. Support terminates earlier upon marriage, emancipation, or military enlistment. For adult children with disabilities who cannot be self-supporting, Family Code § 3910 authorizes support to continue indefinitely.

California's Department of Child Support Services (DCSS) enforces orders through wage garnishment of up to 50% of disposable income, tax refund interception, bank account levies, property liens, and driver's or professional license suspension after 30 days of delinquency. Unpaid arrears accrue 10% annual interest under Code of Civil Procedure § 685.010, with additional penalties of 6% to 72% under Family Code § 4722. Parents owing over $2,500 face passport denial, and willful non-payment can result in contempt charges carrying up to one year in jail.