How California Calculates Child Support: The Statewide Formula
California uses the statewide formula CS = K[HN − (H%)(TN)]. It starts from both parents’ net monthly disposable income and the higher earner’s share of time with the children, applies a K factor that depends on combined net income, multiplies by a factor that grows with the number of children, and adds child care and uninsured health costs.
The formula
Family Code 4055(a) states the guideline as CS = K[HN − (H%)(TN)]. CS is the child support amount; HN is the higher earner’s net monthly disposable income; TN is the total net monthly disposable income of both parties; H% is the approximate percentage of time the higher earner has or will have primary physical responsibility for the children compared to the other parent, averaged across the children if the arrangements differ; and K is the amount of both parents’ income allocated to child support. See Family Code 4055.
Finding K
K equals one plus H% (if H% is 50% or less) or two minus H% (if H% is greater than 50%), times a fraction that depends on TN:
| Total net disposable income per month | Fraction |
|---|---|
| $0 to $2,900 | 0.165 + TN/82,857 |
| $2,901 to $5,000 | 0.131 + TN/42,149 |
| $5,001 to $10,000 | 0.250 |
| $10,001 to $15,000 | 0.10 + 1,499/TN |
| Over $15,000 | 0.12 + 1,200/TN |
The statute’s own example: with H% of 20% and TN of $1,000, K is (1 + 0.20) x (0.165 + 1,000/82,857), or about 0.21.
More than one child
For more than one child, the result is multiplied by 1.6 for two children, 2 for three, 2.3 for four, 2.5 for five, 2.625 for six, 2.75 for seven, 2.813 for eight, 2.844 for nine and 2.86 for ten (Section 4055(b)(4)). Unless the court orders otherwise, the order allocates the amount so that the youngest child’s support is the one-child amount, and each older child’s is the increase from the next lower count.
Who pays
If the formula produces a positive number, the higher earner pays it to the lower earner. If it produces a negative number, the lower earner pays the absolute value to the higher earner (Section 4055(b)(5)). That is why a parent with less income can owe support when the other parent has the children much less than half of the time.
A worked example
Two children. You earn more (net $6,000 a month) and have the children 20% of the time; the other parent’s net is $3,000.
| Item | Amount |
|---|---|
| Your net monthly disposable income (higher earner, HN) | $6,000 |
| Other parent's net monthly disposable income | $3,000 |
| Total net disposable income, TN | $9,000 |
| H%: time you have the children | 20% |
| K = (1 + 0.20) x 0.25 (TN between $5,001 and $10,000) | 0.30 |
| K x [HN − H% x TN] = 0.30 x [6,000 − 0.20 x 9,000] | $1,260 |
| Multiplier for two children | 1.6 |
| Guideline support: you pay the other parent | $2,016 |
The California child support calculator reproduces this example with the same numbers.
Child care and health costs
Employment-related child care and reasonable uninsured health care costs for the children are ordered as additional support, and the court may also order educational or special-needs costs and visitation travel (Section 4062). The basic support is computed first; the additional amounts are then divided in proportion to the parents’ net disposable incomes, with the paying parent’s net income reduced by the basic support and the receiving parent’s not increased by it (Section 4061). In the example, $700 a month of child care and health costs would be shared 57% by you and 43% by the other parent.
What to gather
Because the formula runs on net disposable income, gather pay stubs, tax returns, health insurance premium statements, records of support paid under court orders and child care invoices. The court computes net disposable income itself under Family Code 4059, so accurate gross figures and deductions matter more than a rough net estimate.
The presumption and low incomes
The formula amount is presumed correct and can be rebutted only on the findings listed in Section 4057(b). When the obligor’s net disposable income is below the monthly gross full-time minimum wage, a low-income adjustment is presumed, reducing support by no more than the amount times (minimum-wage income minus the obligor’s net income) divided by the minimum-wage income (Section 4055(b)(7)).
Frequently asked questions
What does K mean in the California child support formula?
K is the amount of both parents' income allocated to child support. It depends on the total net disposable income and the timeshare, and the formula multiplies it by the difference between the higher earner's income and that parent's timeshare share of total income.
What are the K bands in California?
$0 to $2,900: 0.165 + TN/82,857; $2,901 to $5,000: 0.131 + TN/42,149; $5,001 to $10,000: 0.25; $10,001 to $15,000: 0.10 + 1,499/TN; over $15,000: 0.12 + 1,200/TN, each multiplied by one plus H% (or two minus H% above 50%).
How much more is child support for two children in California?
The one-child result is multiplied by 1.6 for two children, 2 for three, 2.3 for four and 2.5 for five.
Are child care and medical costs added to California child support?
Yes. Employment-related child care and reasonable uninsured health costs are ordered as additional support and divided in proportion to the parents' net incomes.
Is the California child support amount rounded?
The statute sets no rounding rule. Court software typically rounds to the dollar, and this calculator does the same.
Official sources
- Family Code 4055: statewide uniform guideline
- Family Code 4057: presumption and rebuttal
- Family Code 4061: allocation of additional support
A local family law attorney can review your situation — many offer a free consultation.
This is general information, not legal advice. It is based on the cited California statutes, rules and court opinions, and every case turns on its own facts. Confirm how the law applies to your situation with a licensed California attorney.