How California Calculates Child Support Payments

California uses a formula, not a fixed amount, to set child support

California does not have a single child support amount that applies to everyone. Instead, the state uses a guideline formula that takes your income, your co-parent's income, and how much time each parent spends with the child to calculate what one parent owes the other. The formula is the same statewide, but the dollar amount changes based on each family's circumstances.

The calculation starts with gross monthly income for both parents — wages, self-employment earnings, bonuses, rental income, and other sources. From that, the state allows deductions for taxes, union dues, health insurance, and existing child support or spousal support obligations. The remaining amount is called net disposable income, and that is what the formula applies to.

California law requires judges to use this guideline formula unless both parents agree in writing to a different amount, or unless the judge finds that explore the formula would be unjust or inappropriate in that specific case. Even then, the judge must write down the reasons why the guideline amount was not used.

Key Takeaways

• California's child support formula multiplies a combined income figure by a percentage that depends on how much parenting time each parent has, starting at 20 percent for the lowest-income parent when the other parent has most of the time.
• Both parents' gross income counts, including wages, self-employment, bonuses, and rental income, minus specific deductions like taxes and existing support obligations.
• The guideline amount applies unless both parents agree otherwise in writing or a judge finds it would be unjust in that particular case.
• The state publishes a statewide uniform guideline, but you can request a local child support calculator or worksheet from your county court to see how the formula works with your numbers.
• Child support continues until the child turns 18, or 19 if still in high school, unless a court order says otherwise.

How the California guideline formula works

The formula has two main parts: basic child support and health insurance and childcare costs. For basic support, California multiplies the combined net disposable income of both parents by a percentage. That percentage depends on how the parenting time is split.

If one parent has the child more than 50 percent of the time (called the "primary custodian"), the other parent typically pays a percentage of combined income that ranges from 20 percent to 25 percent, depending on the exact split. If parenting time is closer to 50-50, the percentage is lower — often around 17 to 20 percent — because both parents are sharing the day-to-day costs. The exact percentages are set by California Family Code Section 4055.

Once the basic support amount is calculated, the formula adds childcare costs needed so the paying parent can work, and health insurance premiums for the child. These are split between the parents in proportion to their incomes. For example, if one parent earns 60 percent of the combined income, that parent pays 60 percent of the childcare costs.

The paying parent's income is then reduced by the amount of basic support owed, and any remaining income is multiplied by a lower percentage (usually 5 to 10 percent) to calculate additional support for the child's other needs. This second calculation prevents the formula from taking too large a share of a high-earning parent's income.

Income sources that count toward child support

California includes most forms of income in the child support calculation. W-2 wages from employment are the most common, but the state also counts self-employment income, bonuses, commissions, rental income, interest and dividend income, and income from trusts or annuities. If a parent receives workers' compensation or disability benefits, those may count depending on the circumstances.

Some income does not count. Supplemental Security Income (SSI) for a disabled child, CalWORKs (California's welfare program), and TANF (Temporary information for Needy Families) are not included. Reimbursements for actual expenses — such as a parent being reimbursed for mileage — do not count as income either.

If a parent is not working, or is working below their earning capacity, a judge may impute income — meaning the judge assigns an income amount based on what that parent could earn. This happens most often when a parent voluntarily quit a job, reduced hours without good reason, or is capable of earning more than they currently do. The judge looks at the parent's age, education, health, and work history to decide what income to impute.

Deductions from income before the formula applies

Not all gross income goes into the child support calculation. California allows specific deductions that reduce the amount subject to the formula. These include federal, state, and local income taxes; Social Security taxes; health insurance premiums for the parent or the child; union dues; and court-ordered spousal support or child support the parent is already paying for another child.

Some deductions are automatic — the court calculates them based on tax tables. Others require proof. For example, if a parent claims a deduction for health insurance, they must show the actual premium. If a parent is paying child support for another child, they must provide a copy of the court order or payment records.

Deductions for voluntary retirement contributions, such as 401(k) deferrals, are not allowed. The reasoning is that a parent cannot reduce their child support obligation by choosing to save for retirement instead of paying support now.

How parenting time affects the amount owed

The percentage of income used in the formula changes based on how much time each parent spends with the child. If one parent has the child 70 percent of the time and the other has 30 percent, the formula uses a different percentage than if the split is 60-40 or 50-50.

California defines parenting time as the number of overnights per year the child spends with each parent. If a parent has 110 or fewer overnights per year (less than 30 percent of the time), the guideline percentage is typically at its highest — around 20 to 25 percent of combined income. As parenting time increases, the percentage decreases, because the paying parent is covering fewer of the child's day-to-day expenses.

If both parents have roughly equal parenting time — usually defined as each parent having between 111 and 228 overnights per year — the formula applies a lower percentage, often around 17 to 20 percent. The exact percentage depends on the specific overnight count and is found in the statewide guideline table.

Parenting time is determined by a custody order, a family law judgment, or an agreement between the parents. If the parents do not have a formal order, the court will look at the actual time each parent spends with the child to determine the split.

Examples of what child support might be in different situations

These examples show how the formula works, but your actual amount will depend on your specific income, parenting time, and other factors. Do not use these as a prediction of what you will owe or receive.

Example 1: One parent earns $3,000 per month, the other earns $5,000 per month, and one parent has the child 80 percent of the time. Combined gross income is $8,000. After deductions for taxes and other items, net disposable income might be around $6,500. The guideline percentage for 80-20 parenting time is approximately 20 percent. Basic support would be roughly $1,300 per month, before adding childcare or health insurance costs. The parent with 20 percent of the time would owe this amount, adjusted for their share of childcare and insurance.

Example 2: Both parents earn $4,000 per month gross, and parenting time is 50-50. Combined net disposable income might be around $6,500 after deductions. The guideline percentage for 50-50 parenting time is approximately 17 percent. Basic support would be roughly $1,100 per month before adjustments. Since parenting time is equal, the formula may result in little or no basic support owed, because both parents are sharing costs equally. However, one parent might still owe a portion of childcare or health insurance costs if those are not split equally.

Example 3: One parent is self-employed and reports $10,000 per month in business income; the other parent earns $2,000 per month in wages. The lower-earning parent has the child 90 percent of the time. Combined gross income is $12,000. After deductions, net disposable income might be around $9,500. The guideline percentage for 90-10 parenting time is approximately 20 percent. Basic support would be roughly $1,900 per month, plus the higher-earning parent's share of childcare and insurance. The higher-earning parent would owe this amount.

Where to find a child support calculator or worksheet

California provides a statewide uniform guideline that all courts must use. You can view the guideline in California Family Code Section 4055. Many county courts also provide a child support calculator or worksheet on their websites that lets you enter your income and parenting time to see what the formula produces.

To find your county's calculator, search "[your county name] child support calculator" or visit your county court's family law self-help center website. Some counties have interactive online tools; others provide a PDF worksheet you fill out by hand. These tools are free and do not require you to create an account.

If you want a more detailed calculation that accounts for all deductions and adjustments specific to your situation, you can ask a family law attorney or a court-approved mediator to prepare a child support guideline calculation form. This form is often called a "Guideline Calculation Worksheet" or "Form FL-1150" in some counties.

When child support ends and how amounts can change

Child support continues until the child turns 18, or until the child turns 19 if the child is still in high school full-time. It also ends if the child gets married, enters active military service, or is declared emancipated by a court. If a child has a disability, a parent may request that support continue beyond age 18.

The amount of child support can change if either parent's income changes significantly, if parenting time changes, or if childcare or health insurance costs change. Either parent can ask the court to modify the order by filing a request for modification. The court will recalculate using the current guideline formula and the new circumstances.

In California, child support orders are reviewed every three years automatically if the case is handled by the Department of Child Support Services. If the case is private (between the parents and their attorneys), either parent can request a review at any time if there has been a material change in circumstances.

Frequently Asked Questions

What if one parent makes much more money than the other?

California has a high-income cap in the guideline formula. If combined net disposable income exceeds a certain threshold (which changes yearly but is around $250,000 to $300,000), the court may explore the guideline percentage only up to that cap and then use discretion for income above it. The judge must consider factors like the child's standard of living, the parents' ability to pay, and the child's needs when deciding how much additional support to order above the cap.

Does child support change if I lose my job?

If you lose your job involuntarily, you can ask the court to modify the child support order. The court will look at whether you are actively searching for work and what income you could reasonably earn. If you voluntarily quit or reduced hours without good cause, the court may still impute income based on your earning capacity rather than reducing your support obligation.

Can parents agree to a different amount than the guideline formula says?

Yes, but the agreement must be in writing and signed by both parents. Even then, the judge must review it and find that it is in the child's best interest and not the result of duress or unequal bargaining power. If the agreed amount is significantly different from the guideline, the judge may ask why before approving it.

Does child support include money for the child's college education?

The guideline formula does not automatically include college costs. However, California law allows a judge to order a parent to contribute to a child's college education expenses as part of a child support order, but only if both parents agree or if the judge finds it is just and equitable. This is separate from the basic child support calculation.

How do I know if the amount being paid is correct?

You can use your county's child support calculator or worksheet to check the math yourself, or you can ask a family law attorney to review the calculation. If you believe the amount is wrong, you can file a request to modify the order and ask the court to recalculate. The court will use the current guideline formula and your current circumstances.