How California Child Support Is Calculated
California uses a mathematical formula that considers both parents' circumstances. Unlike simple percentage models, California's formula considers both parents' net disposable incomes and the amount of time each parent spends with the children. The formula is:
CS = K × [ HN − (H%) × TN ] Calculate net disposable income for each parent
Gross income minus federal tax, California state tax, SDI (1.1%), Social Security (6.2%), and Medicare (1.45%).
Determine TN (Total Net) and HN (High Earner's Net)
TN = combined net income of both parents. HN = the net income of whichever parent earns more. H% = that parent's custody timeshare.
Calculate K factor
K = child_percentage × (1 + H%). Child percentages: 20% (1 child), 25% (2), 30% (3), 35% (4), 40% (5+).
Apply the formula and add mandatory add-ons
Work-related childcare and uninsured health costs are typically added to the base amount as mandatory add-ons.
| Children | Base % | K at 0% time | K at 20% time | K at 50% time |
|---|---|---|---|---|
| 1 | 20% | 0.20 | 0.24 | 0.30 |
| 2 | 25% | 0.25 | 0.30 | 0.375 |
| 3 | 30% | 0.30 | 0.36 | 0.45 |
| 4 | 35% | 0.35 | 0.42 | 0.525 |
| 5+ | 40% | 0.40 | 0.48 | 0.60 |
California Child Support — Frequently Asked Questions
California's child support formula is CS = K[HN − (H%)(TN)], where K is a multiplier based on the number of children and the higher earner's custody time, HN is the higher earner's net monthly disposable income, H% is the higher earner's approximate custodial time share, and TN is both parents' combined net income.
Yes. California uses an Income Shares approach. Both the paying and receiving parent's incomes are factored into the formula. A parent who earns significantly more will generally pay more, but the other parent's income also affects the final amount.
Custody time (H%) has a direct impact on the California formula. The more time the higher-earning parent spends with the child, the lower the support obligation, because they are directly absorbing more of the costs during that time. This calculator lets you input the estimated custody timeshare.
California deductions include federal income tax, California state income tax, State Disability Insurance (SDI, 1.1%), Social Security (6.2%), and Medicare (1.45%). Health insurance premiums paid for the children, mandatory union dues, and certain other job-related costs may also reduce net disposable income.
California does not have a fixed income cap like Texas. The formula applies to both parents' full net incomes. However, for very high earners, courts have discretion to deviate if the guideline amount would result in a windfall unrelated to the child's actual needs.
DissoMaster and Xspouse are commercial software programs used by California courts and attorneys. They apply the same K formula but include additional refinements (exact tax calculations, hardship deductions, add-ons). This calculator provides a good estimate but the licensed software will be used in an actual court proceeding.