Family Court Playbook · Step 6 of 12
How Child Support is Calculated in California
Understanding the guideline formula, income factors, and how timeshare affects your amount
Quick answer
California calculates child support with a statewide guideline formula in Family Code section 4055, based on both parents' income and the percentage of time each parent has the children. The guideline result is presumed correct, and a judge departs from it only in specific situations. You can estimate your number with the free California guideline calculator.
What is guideline child support?
California uses a mathematical formula (Family Code § 4055) to calculate child support. The formula considers both parents' income, the percentage of time each parent has custody, tax filing status, and certain deductions. The result is called “guideline” support.
How the formula works
The formula: CS = K[HN − (H%)(TN)]. K is the amount of both parents' income allocated for child support. HN is the high earner's net monthly disposable income. H% is the approximate percentage of time the high earner has the children. TN is the total net monthly disposable income of both parents. The court almost always orders guideline unless there is a reason to deviate.
The guideline formula
Income and timeshare determine the amount
Guideline Calculator
What affects the amount
Income of both parents (gross and net), percentage of time with each parent (timeshare), tax filing status, health insurance costs for children, childcare costs, and other children from other relationships all factor into the calculation.
Try the calculator
How to modify an existing order
If circumstances have changed (job loss, raise, change in timeshare), you can file an RFO to modify support. The court looks at current income, not what was true when the original order was made.
Judicial discretion
Common questions
How is child support calculated?
California uses a guideline formula based on both parents' income and the timeshare split. The formula is in Family Code § 4055. Use our free calculator to estimate your amount.
When does back child support start in California? (Retroactive support and the date of filing)
In California, child support can be ordered back to an earlier date, but the start date is usually tied to a specific event in the case rather than the day someone first reached out for help. Here is how that generally works.
What can I do if the other parent violates our custody or support order?
You can ask the court to enforce the order. Contempt (forms FL-410 and FL-411 or FL-412) is one option, but it is quasi-criminal and the judge must find the other parent knew the order, could comply, and willfully refused. For many issues a Request for Order (FL-300) to enforce, make up time, or set wage garnishment is faster and less drastic.
Watch this explained
How child support is generally calculated
Calculate yours
Use our free California guideline calculator to estimate your child support amount.
Open the free calculatorA family law attorney will always have the biggest impact on your case. If you can afford one, we encourage you to hire one.